TPTK w/ nut draw

1/2 live game. Villan and I have a lot of history. weve played 2 or 3 huge hands and I'm up about 250 vs him. We've also played many medium sized pots whee weve bluffed each other out. Basically we've been playing super aggressive vs each other hes been folding more than he is accustomed to and int liking it.

Villan raises to 12 in EP. One caller. I call w/ AQ of diamonds. Button calls and we see the flop 4 handed.

Flop: Q64 w/ the six and four of diamonds. Villan pots it w/ $45. (This is abnormal all follow through bets to this point have been 1/3 to 2/3 of the pot). Villan has 300 more behind and I cover.

My read is that villan is strong here. I put him on AA or KK. He is trying to play a big pot. I also feel that any raise here would not be respected and he would push w/ AA or KK. I call the button folds.

The turn blanks off and Villan fires 75. I call.

The river blanks off and Villan fires 75.

At the table I felt that calling and getting paid when I improved was the most positive EV. In retrospect im not so sure.

1) Whats the best line for the flop?
2) Whats the best line for the turn as played.
3) Is the river a clear fold?
Thanks in advance.

[Big_Jim]

I like your line.

You let him hang himself if he's behind, but he's probably not.

You have a strong draw, and odds (+implied) to continue on flop/turn.

Hard to fold on the river with those pot odds, though. Maybe he has AK/KQ/JJ?

I called he showed down KK.