25NL: KK OOP 3bet Multiway Pot

http://weaktight.com/1324427

BU is 56/4/0.9 over 49 hands w/ 40% (5 hands sample) fold to cbet
Only 2 hands on MP

$0.1/$0.25 No Limit Holdem
7 players
Converted at weaktight.com

Stacks:
UTG ($14.75)
UTG+1 ($25.00)
MP ($53.50)
CO ($8.00)
BTN ($37.30)
SB ($25.00)
Hero (BB) ($25.00)
[UTG+1 posted $0.25]
[CO posted $0.25]

Pre-flop: ($0.85, 7 players) Hero is BB :ks: :kh:
1 fold, UTG+1 checks, MP calls $0.25, CO checks, BTN raises to $0.75, 1 fold, Hero raises to $3.25, UTG+1 folds, MP calls $3, CO folds, BTN calls $2.50

Flop: :8s: :9c: :ac: ($10.35, 3 players)
Hero checks, MP checks, BTN bets $2.50, $2.50 to Hero ($21.75)?

1) How is my 3bet-sizing here?
2) How big of a mistake was it NOT to "cbet" here (it obviously got me into this spot)?
3) Is BU's bet ever a bluff here?

Assuming We Called
4) What is our plan if MP folds and a rag peels on the turn?
5) What is our plan if MP calls and a rag peels on the turn?

I think the 3b size is good vs. fish
I would cbet because the fish will peel a lot of draws, 9x and still probably calls with QQ-TT because they feel like big hands

if we call here, just proceed with caution and I wouldn't call any more than like 1/3 pot on the turn

Yeah given his fishiness, there's no reason to think he'll barrel a turn with any range that we do remotely well against, c/f turn.

Flop (3) - In my experience if these stationy fish ever do bluff, it's usually a retarded small bet like this. i mean not saying we're ahead of his range here, but getting 10/1 there's enough chance this is a bluff or some randomly pointless fish bet with like 1010 or something to peel. Especially when we expect him to play straigthforwardly and fishy on the turn and river.

3b sizing is fine, now c/f flop.

For god sakes, don't fold!