Betsize on river (if it's a bet)

[Kjell201]

Prima , .5/1$ NL 6-max

I get A [img]/images/graemlins/spade.gif[/img]K [img]/images/graemlins/club.gif[/img] in the CO.
2 folds, I make it 4$, btn folds, sb makes it 13.5$, bb folds, I call.

I started the hand with 110$ and sb with 85$.
Anyone do anything different so far? (Villians 2nd hand at the table, no read)

Flop: A [img]/images/graemlins/diamond.gif[/img]2 [img]/images/graemlins/heart.gif[/img]4 [img]/images/graemlins/heart.gif[/img]
Pot 27$
Villian bets 13$, I just call. Is just calling ok here? I figured that if I raise I let him get away with KK/QQ too easy and by calling I can make it look like I'm on the flushdraw and he might continue to make me "pay" for my "draw".

Turn: 8 [img]/images/graemlins/heart.gif[/img]
Pot: about 50$
He checks, I bet 20$.
Comments?
He calls.

River: 8 [img]/images/graemlins/diamond.gif[/img]
Pot: 90$
He checks. Hero ???
I made a small bet of 26$, no idea why I picked that amount. If villian calls he will have 13$ left so should I just make it 40$ and put him all in? It feels like if he's calling 27$ he's calling 40$ aswell and that way I "waste" 13$ whenI have the best hand by not making him pay his whole stack.
Does anyone check behind btw?

Thanks