1) My guess is he either held KK or more likely AA because you played the hand fine..
2) You're not going anywhere from this hand given how much more is it for you too call.. it's a bummer you don't have , but still, fine..
3) your flop raise should be putting him all in not letting him off for those $3 extra..
4) if he is loose and passive then i think this is a good fold, but still, I think you should bet turn because he can be calling you with a J as well, being so loose and passive as you suggest..

1.
His 3bet sure looks like AA/KK, and the flop check just SCREAMS "SET!" but, if he has KK then it's a cooler and I stack off. I just can't fold the turn because I'm stacking off on that flop so I don't particularly care how he plays the turn (especially if it blanks). Oh, and 30/7 is NOT aggressive, he's loose passive. What are his AFs?

2.
He's short, you have enough of your stack in to call.

3.
Good line, but just CRAI and get it over with.

4.
If he has JJ, then he made enough of a mistake pf for you to stack off at will...if he has a K, then he made BOTH a big enough preflop AND on the flop for you to just shove the turn.

1. Standard. I have a feeling the river didn't help your cause, but unless he has KK you got your money in good, which is all you can do.

2. Standard against a shortstack. You're definitely ahead of his shoving range (he's stacking off with 88+, as well as any lone /[Kd], even if you may not be ahead of his specific two cards.

3. Again, standard - but just put him in on the flop. All the money is going in no matter what turn card hits, so just get it over with.

4. Tough spot, but after you check the turn, you have absolutely no idea if he has a King or not. I'd be really tempted to look him up with him betting less than 1/2 pot like that.

I'd bet 30 to let a draw make a mistake...it's equivalent to a shove if he has you beat, but it gets more hands that you're ahead of call than the shove (a bare FD may fold to a shove, but call 30, whereas any K hand is getting all in no matter what).