lets play "pick a good bet size" ! (a bluff)

[BobboFitos]

3handed Wynn 10-20, I am shortstacked with 10k. mikech has 15k and peachykeen (drunk) has more. mike raises his button to 60, peachy folds, i make it 220 with 42[img]/images/graemlins/spade.gif[/img]

mike raised his button (we only played 30 mins, and during that time, we got 30 hands or so? maybe more? he folded his button twice, then I thought he brought in ~75% vpip or so otb) the previous 3 opens peachy and i folded our blinds, so clearly i was ready to 3bet.

my read on mike is he's nitty postflop, but preflop he doesnt fold to 3bets. literally, we've logged a good deal of live play together, and during that time ive probably 3bet him 75 times, and he's folded maybe 10 or 15 times. time and again ive said, 'mike, you are too loose to my 3bets, try a fold, it will save you money, rather then folding the flop".

the flop nails me, 7[img]/images/graemlins/club.gif[/img]6[img]/images/graemlins/spade.gif[/img]3[img]/images/graemlins/club.gif[/img] (~450$) I bet 300. mike calls. turn is a J[img]/images/graemlins/diamond.gif[/img], I check, he checks. River is a Q[img]/images/graemlins/diamond.gif[/img]
1. Should I bluff?
2. What does he have?
3. What should I bet?

keep in mind we are very deep, mike did not raise the flop nor did he bet the turn. there is 1050 in there.