Thanks for the very detailed report. I would say that most of the problems are related to playing on mobile, the game was only designed for pc. I am actualy amazed that you managed to play it on mobile.
About farming stats it is locked, you can only increase them so much via training and this limit increase a little with each level up.
During the fight you draw new cards every 3 turns, it does not depend on the skill selection.
The game started with art draw by my sister but she stopped drawing and I went to AI art, all sex illustrations are AI art.
The enemy levels vary with victory and defeat, they win they lose a level, if you win they gain a level, it is not very realistic, but it works to create balanced fights.
Some of the bugs you found are already fixed on the next version but Shion story case I have no idea what could be wrong none had problems with it until now.