You can't have too many bad points, the cutoff is that Ash needs to still be wearing her "good outfit" by the time she first meets him in the gym, that way she can give him a polite response and that leads to him hiring her during the interview.
After that you just need to accept Ryan's advances during the work events and be single during the endgame to get his ending.
EDIT: I think the relationship ending only happens if Ash is still wearing her "good outfit" by the endgame, otherwise she just has casual sex with her boss.