About exploits - I've tried various balance options and decided to stick with the current one. I don't want to scare players away with difficulty. But there will be more challenging levels in the future.
About harem ending - I thought you'd only be able to help one girl (and maybe fulfill one negative reqirement to other girl), but with the balance like this, I think we should consider that outcome as well.
About game crash - I haven't encountered opening a store crashing the game. Can you describe what happened in more detail? What did you do step by step, and what happened in the end?
Thanks for feedback !