Valuebetting weak PP in 3bet pots?

[chinz]

I don't have a HH for this, but I think that I've been losing a lot of value on these hands... (especially on example 2)

If I am playing someone who plays decent preflop, but is a bit too call-happy postflop (and/or my image is very aggro), should I bet river for value in spots like this:

Let's imagine he is playing something like SB VPIP 75, F3bet 80% and FCbet 30%. Because he is folding a lot to my 3bets, my 3betting range is about 12-15%.

He opens from the button, I 3bet with 66 and he calls.

Flop: 379 (two tone)
Hero cbet, he calls.

Turn: 3793 (not filling any draws)
Hero checks, he checks

River: 37932 (FD missed)
Hero ?

At this point he should almost never have a better hand (unless he has exactly 88), so shouldn't I bet this river for value against A high or strong K high. Every draw missed, so a villain like this might try and make a hero call (not understanding that bet-check-bet line from regular in 3bet pot is almost always thin value)

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Example 2:
The exact same situation, but I have AK. I know a lot of good players (in higher stakes) take 2 streets of value with strong A highs, would this be a good spot for it or is it too marginal?

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I would bet with 66 against this villain type, but valuetowning someone with strong A high is something I should probably practice more.