About Kate, after following the slutty route, anything interesting at the cafe seems to stop happening.* (The several slutty scenes with Kate were fun.) Not sure if there's a second chance to switch to the slutty club (not sure if I want to, but I am curious))
*Though my character did get a pay raise.
Things with Violet seemed to end after the "spa date".
Maybe better luck with Alice or Olivia.
About Alice, I encountered her somewhere in the school and she invited me to meet her at the arcade, but nothing happened when school ended.
BTW, on a separate path, I said yes to Damian to be his girlfriend, then after that I rarely encounter him - only had one more date after that - so far.)
And, on a third path, I chose to work at the bakery. There, things stopped being interesting after I declined the boob job.
Other than almost being fired at the cafe, I don't see any way to quit a job - except stop showing up, which seems rude to me. (Just because I decided to play a slutty character doesn't mean she has to be rude, too)