When it comes to the payment issue; I would tackle that IMMEDIATELY. That way you set the tone for the future, if there ends up being one. I absolutely hate talking to people/ reminding/ nagging about fees. I hate that more even than talking to parents about kids behaviour issues, lol.
When it comes to his behaviour; again, set the tone RIGHT NOW. My handbook discusses the fact that when you are on my property, MY rules apply. If mom isn't dealing with it; and it probably is because she's embarrassed, then I would be. I have a 5 y/o that still acts up sometimes when picked up (especially by mom). When I noticed that she wasn't saying anything, I started to. He would whack his mom in the stomach when she would say she was making something for dinner that he didn't like!! I was horrified. In the usual, firm voice that I would normally use to reprimand, I began to remind him that we do not use our hands that way, to anyone, Mommies included. And that his mom's presence did NOT change our rules. Really, I was sending a message to mom that she begin to control her child or I would. Pick up goes much more smoothly now.
I think my threshold for tolerance extends to about a month, perhaps more like 6 weeks if the child is part time or inconsistently attending. I try to remember that as trying as it is at the beginning, kids do learn fairly quickly that certain behaviours are tolerated at home but not at daycare. However, as always, the bottom line is: if it's making you (and therefore everyone else, haha) miserable, then it's not worth it. Your home, your rules, your happiness.