Last 3 hands of night.  I have around 80k to start the hand Christian (charder30) covers.  I had been relatively quiet in general, but had 3b Christian twice during the day (he had been opening frequently), one hand I double barreled K22ddQcc, and another hand I checked down J78hhQJ and lost to 75dd.  He saw my hand neither time.  

I rz 44 utg at 250/500/50 to 1200 btn defends charder defends BB.  Flop 664ss, chks through. Reasons for checking this flop was because I thought btn was likely to fire given his style of play and my perception of his range.  I also thought I induce a lot of action on various turn cards.  Turn 2s, so 35ss is the nuts.  6642sss. 

Charder donks 2500 I make it 7500 he calls.  River 2 he leads 13.5k.  What is the best play and why?  

Thank you,

gaucho2121/david