Hey
Thank you so much for this comprehensive feedback, it truly helps the game. I have to say that your drawing looks AMAZING!!! I never expected anyone to make fanart of my game! Thank you!
The burping is going to be way more dynamic. She will make noises in the next update. Stomach growling is something I've wanted to add aswell.
Adding numerical value to the food is a good idea. Tbh even I don't currently know how much each food actually gives you.
The missing bubble is a bug I'm already aware of. It comes because after the inflation minigame is over, it removes all the UI on the screen including the bubbles. I'll probably fix it at some point.
I've already reworked the UI (not released though). I think it's a bit cleaner and the locks look more interactable.
I'll remove the spam click on the minigame.
I'm planning on making the max limit even bigger. I've already made the corresponding stomach widgets.
Although the current plan is that you're able to push your limits with bloat pills and drinks, which also have 4 different sizes
The NPCs are also going to be feedable, that's when you can force them to eat as much as physically possible. They're also going to have little randomized dialogues when stuffing.
Random encounters for stuffing is quite an interesting idea. But I wouldn't even know how to pull it off without it getting tedious after a while. Either way, some kind of a random event might actually be interesting. Or making the NPCs just walk around might make the world feel more alive.
I've changed up the scaling area. Now you're able to lock the stats wherever you want. Might break the story because it's about gaining weight over time. But in general I feel like making proportions customizable is what's best for the game. (you're finally going to be able to have huge tits! Yaaay!) 
The devil isn't going to stay that size in the full game. I just kinda rushed the version out and didn't really bother to change her back.
I have no idea what might cause your error.
The double Arabella thing is sth I've overlooked.
That's a good thing you pointed out how most of the games here are unfinished. It's something I've noticed too but I totally understand why it happens, it's so hard to not add these new ideas in. My game is already ten times the size I planned. I really hope to just finish the game.
Again, thank you for taking the time and for drawing this awesome fanart! That is really cool of you, I love it so much! How long did it take?