You can call them to a date location and not actually start the date, just leave them sitting there. That sort of resets the "time since last date" timer.
I don't know if it's possible. I guess the only thing you could do is not get their number and hope you run into them again later and maybe they won't want to flirt with you?
87.5 million is, in fact, the current max number of fans. If you finish a gig or if you're supposed to go to Simon's office, it's normal for him to call you every time you leave somewhere. Maria and Kim very rarely call, and only as part of a quest.
As of right now, the max number of fans is 87.5 million. If you're at that amount, you can't currently gain any more. The limit is usually raised with each update, though.