Thank you for the suggestions! I know the game is in quite a bad shape and that is mostly due to my incompetence in coding. As for the art, please keep in mind that making multiple different ways to display growth requires quite a bit of artwork. I have discussed with the artist a few ways we can implement such multi-dimensional growth, but we are still working on it.
I totally understand. It will be very difficult, but it is critical - absolutely worth pushing your knowledge and skills to do. Muscle level, eyes, Hair, funparts are all first starts. Perhaps integrating live DAZ-model rendering into the game is worth doing. (See: Certain TWINE/Sugarcube Projects using webgl to do this.)
Incompetency is not the same as ignorance. Games are very hard with all manner of use-cases. Players are mashing buttons, opening and closing menus - changing the state of the game and its systems as fast as they can push buttons. Something is bound to break. You just learn what gets broken and put in the guards and controls to deal with it.
For now - outside of that technology - just keep planning, structuring, and implementing pieces of variation, surprises, fun stuff, and dialogue. You have something here. Work hard, and just keep improving.