Thank you for enjoying the game and taking the time to write your opinion and suggestion, before responding, as well, I want to tell you that I'm really happy my game can give you the feeling that a sandbox game is supposed to give. I'm happy that the characters feel alive and that you can introduce yourself into the game through the MC. Now, to address your points.
1.Your idea is nice at first but it has its downsides as well. First of all, there has to be a clear definition of "view each scene/get every interaction that the character" does that imply every variation of every single scene that that girl is part off? Even the ones where she's not the main girl of the scene, and it's a side character of others girl scene? The player won't be able to keep track of that and it can get annoying pretty quickly as well. The solution to that is that I would have to keep track of every single scene the player is watching and handhold him into finding each and every single one of them, which is something I don't want to do. And the second flow, which is the main reason. I try to give a reason to everything I add in the game. The pointing system isn't just a mechanic in the game, it's a system that is present in the game itself, that the MC and Mhyrorin are aware of. The point of the game is to corrupt the girls by certain methods. If for a girl the best method is to be nice and sweet but a bit pervy and push the limits little by little, you shouldn't be allowed to lvl her up (and in consequence make her love you more) by only being a perv, or an asshole and so on. There would be a time where you won't know for sure what you have to do to raise a girls stats, and you'd have to try out different methods, see which one works and so on. So it's more than just a mechanic in the game, it has it's own identity within the games world. I get that the mechanic could get a bit annoying, but I don't mind that. I think that some things should be a bit annoying, but of course it is a fine line that you have to navigate. I agree with maybe tweaking the numbers to make it less annoying, and I waited and wanted to hear that feedback from the players, to maybe find a sweet spot for the stats, but I haven't heart that yet.
2. This being a porn game, it's not supposed to challenge your believes on life and reality itself, or make you study hours to pass a puzzle or smth like that. But with that being said, I don't agree with this statement "remember that this is a porn game, it's not really supposed to be challenging or make you think" It's porn, but it's also a game, and I think any game should give you any kind of challenge or make you think at least a little. You have lots of other options that give the player the satisfaction of being able to just kick back, watch some porn, and rub a quick one (or a long one idk). But from the first point, and the second one together, it just seems like a normal visual novel with a few extra clicks. The endpoint would be to just remove the sandbox completely. Add that to the absence of a walkthrough and it feels like I've made the dark souls of porn games, which would be a compliment I guess, but I don't think my game is that hard.
3. When I first started the game, I would have agreed with you. I wanted the main focus to be the incest, and in consequence, of course, the family. As I developed the games story, I changed my perspectives a little, and I don't view it as an "incest game first" anymore. But since I first made the plans with the incest being the priority in mind, for a while it's going to be. Meaning that the first girls to receive a lvl 2 will be the family. I don't want you to think that the mom and sister will be a distant afterthought, just that, the girls that make the more sense will get the most attention. I'm sorry I can't get into a lot more details regarding this point, since I don't want to give spoilers, but what I can say is that the most important girls in the MCs life will get the most attention, and his family is part of that group, but a couple of girls will be as well. Regarding the school, I explained this point before but I'll try to explain again. Let's imagine I didn't add the school and focused on the family like everyone asked. Let's say I take Isabella to lvl 3 or 4 and at that point she maybe kisses the mc without any care, maybe she show herself naked to him without caring, etc. And after that, I add the school, and the MC goes to school for the first time. In the games timeline, you should go to school for the first time while all the girls are lvl 1. And now, from an update to update players perspective, you just shoved your tongue down Isa's throat a minute ago, now you go to the school and she doesn't let you touch her leg. And that's a thing I really disliked about a lot of games I played. An option that is not really an option would be to add the school with the first 4 lvls done from the start, which is not really duable, but you can say, just make her scenes to lvl 4, but then again, she has a lot of shared scenes, what do I do there? And a lot more of this kind of situations that I have to take into consideration. I have to find a way to balance the players that play update to update, since they are the ones subscribing to patreon, and of course I have to show consideration to them too, but I have to keep in mind how the game would look to someone who starts playing half way through the games development, or even when it's done.
4. On this one we pretty much both agree, and I believe that the MC, although the game is still early and I didn't have the time to flesh out his character more, has a pretty colored personality, and is not too one dimensional. So on this point I don't have much to add besides that, only a thank you for liking how the interactions between the chars go and their personality, I work a lot to flesh them out as best as I can.
5. My thoughts align with yours as well on this one, and I'm really happy you know what a slow burn is. It's actually rare apparently. To give a bit more details on this, the slow burn will be as slow or fast as it makes sense for the characters. Some maybe will be harder to corrupt, some easier. It won't be a set thing, where for all the girls, let's say lvl 3 or 4 means they kiss the MC. The progression will advance based on if it's something logical for the girls to do or not.
6. My explanation on point 5 pretty much implies that I don't want fixed things to happen on lvls, so it kinda invalidates your ideas. Sorry about that. I read all of them, and they are good ideas, maybe I will add them, but not on set levels.
7. Sadly, a toggle for public hair wouldn't be as easy for a game in renpy, with scenes made in honey select as it would be in other games. Just that toggle would mean at least twice the renders, and maybe even new special scenes that would focus around the public hair, so that's not something really duable. I'm sorry, but for now it's a no on that one. Maybe I will change my mind in the future
8. This point invalidates your 5th point as well, and it's pretty much what I answered at 6. The progression will be tailored per character. Meaning it won't go the same for every one of the girls. For some will be faster, for some slower, for some will have extra steps, for some will skip a few. Some girls will get corrupted to a certain point, and others far beyond that point. Again, I will do what feels more logical for each of the girls
9. Besides what I already answered at the point 3, to add to that and respond to this one, not just the family, but most of the girls will keep their personality throughout the corruption. Not just the family, but most of the girls, there will actually be quite a few who will go into completely mindless slut mode. I am trying to build their personalities as best as I can, trying to avoid having them 1 dimensional, and give them depth. And I don't want to lose that. So yes, they will "full on bimbo cum-hungry sluts", not just the family, but most girls. A "full on bimbo cum-hungry sluts" is nice to have every now and then, so some girls might, but just a few.
Okaaay, I think I answered everything I hope. I wrote to much to double check the writing on that, so sorry for typos and bad english. Sorry if it was too long, but you put so much effort into your feedback, I thought it would've been respectful to respond in the same detailed way. Sorry if I came across mean, or maybe combative, but it's just the way I phrase things, try to read it in a delicate voice if it helps

. And uhhhh, I don't know what else... I hope you're happy with my responses, I hope where you don't agree we can agree to disagree and thank you again for taking time out of your day to help me improve the game. This is the whole reason I released it so early into the development and thanks to people like you I can improve my way of working and the game itself. And thank you for liking the game!
TL;DR
People go "sandbox bad" but then play sandbox wanting just visual novel. I go sandbox good!
Game is too hard! I don't think it's too hard!
This is an incest game, focus on family! - I don't view it as just an incest game!
MC personality kinda nice! - Thank you!
Keep the slow burn! - oke
Pubic hair toggle! - too small effort to reward ratio, sorry.
Don't have an endgame where they are all "full on bimbo cum-hungry sluts" - oke