200NL HUCASH top pair four straight board against a degenerate bluffer

[Vinetou]

PokerStars No-Limit Hold'em, $2 BB (2 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

Hero ($2639.30)
Button ($302)

Preflop: Hero is BB with A[img]/images/graemlins/club.gif[/img], T[img]/images/graemlins/diamond.gif[/img].
<font color="#CC3333">Button raises to $6</font>, <font color="#CC3333">Hero raises to $20</font>, Button calls $14.

Flop: ($40) 3[img]/images/graemlins/heart.gif[/img], 2[img]/images/graemlins/diamond.gif[/img], 4[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $28</font>, Button calls $28.

Turn: ($96) 6[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $72</font>, Button calls $72.

River: ($240) A[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">Button bets $144</font>, <font color="#CC3333">

<font color="black">Villain is degenerate bluffer. He donked like 1000$ to me by bluffing his whole stack at me a lot of times. He looks for opportunities to make creative bluffs, to try to push of a top pair in a reraised pot and stuff like that. Also, he knows you are trapping, but he will still bluff his whole stack because he can't help himself. However, he changed gears in last 15 minutes a little bit and I even caught him checking down ace high. So he changed gears a little bit, but I don't think that he changed his style too much.

I should explain my flop and turn play first. I made a c bet on the flop, pretty normally. If villain had a 5, I am 90% sure he would raise me on the flop, so I figured 6 was a scare card for him and I decided to fire second barrell to try to push him off something weaker. He made a bet on the river, which confuses me. Even though he might be bluffing, I don't know what I can beat. He is capable of turning one pair into a bluff, but I am more afraid of a two pair value betting here. I just don't know what hands would he call me down twice which I beat. And he is capable of calling you down twice light, just too see if you check river so that he can bet (but he changed gears, so he probably wouldn't do that here, or maybe, I don't know).

If I didn't catch the ace, I would actually fire a third barrell here, because he is not slowplaying.

So do you call here?</font>