PFR w/55 - flops OESD

[Sadat X]

Party 2/4 NL 6max

Button's stats are 45/6/1.3 over 125 hands. The guy is basically unbluffable postflop, and has no problem calling flop bets with middle or bottom pair, even with big cards on board. I'd also seen him call the river w/A high after the aggressor checked thru on the turn.

SB is 37/11/2 after only 40 hands.

Hero has $640
Button has $540
SB has $400

Folded around to hero, in the CO with 5 [img]/images/graemlins/diamond.gif[/img]5 [img]/images/graemlins/club.gif[/img]

Hero raises to $14, Button calls, SB calls, BB folds

Flop ($48): 6 [img]/images/graemlins/heart.gif[/img]4 [img]/images/graemlins/spade.gif[/img]3 [img]/images/graemlins/spade.gif[/img]
SB bets $25, Hero raises to $75, Button calls, SB folds

Turn ($223): 3 [img]/images/graemlins/diamond.gif[/img]
Hero bets $123, Button calls

River ($469): K [img]/images/graemlins/spade.gif[/img]
Hero checks, Button goes all-in for $320, Hero folds

Three questions:

#1 - This seems like an obvious flop raise, what about the amount?

#2 - Should I even be betting this turn? Seems like button isn't liking his hand any less at this point.

#3 - Is there any value whatsoever in making a blocking bet on the river? What if it's the K [img]/images/graemlins/diamond.gif[/img]?

All other comments appreciated as well.