Rules and clarifications in AC

A couple questions, sorry for the longish post.
1.) What is the purpose of not being allowed to receive chips from a player just prior to sitting? A friend owed me $200 for the room, and I went to sit down at same table. He offers me the money in chips. Table tells me I can pay him for them but not just take them. If this is to stop collusion wouldn't it be more helpful to see this and keep an eye out for team play?
2.) I sell 40 in chips to a woman at table. I am playing 2/4 with about 250 (it was a decent session) in front of me. I go to put the money in my pocket and am told to leave it on table. This was between hands. I am told you don't want short stacks doing this, but why? I like to play people that don't have the money to make correct plays. And since it was between hands, is this different than tipping the server with a chip?
3.) There was a huge argument regarding a side pot. This is 2-4 limit. On turn, in three way pot, one player is all-in. Side pot gets created. Dealer puts main pot in front of all-in player and side pot in middle of table. One man in hand objects saying it goes the other way. Huge fuss, floor comes over and rules in dealer's favor, saying thats how Caesars does it. Argument ensues. Bitchy man complains, then all-in player (who loses) starts in. Bitchy man says he will call casino regulators and complain. Is this not how the pots go? And why would the regulators care?
4.) Told you this was long. Last one though. 3-6 limit. I hit the nuts on the turn. Bet out six. Player after me raises 2 (all-in) next guy calls. Action back to me. I try to complete/raise (I ask what my options are). The dealer tells me that to raise the all-in player would have needed to bet at least half the bet (three). I say ok, I'll complete to 12. Dealer says no. I let it drop. Turn comes, I bet, other guy calls. River pairs board. All-in completes boat wins the pot, I win the side pot. The ruling cost me money, but really I just want to know if that is the rule.