I think 3xbb raise is fine for 6max when you're first in, unless people at the table will call large preflop raises with junk (which might be the case considering this guy's 64 call). I think you gotta lay it down or raise it big on the flop here. Smooth calling a roughly pot-sized bet with just ace high and two overs is fairly loose-weak. After the ace comes on the turn, I am just calling it down too, so I wouldn't say you neccessarily misplayed it there--no reason to take him out of the lead if he's bluffing or donate more money if he's beat. Really, the only way you could avoid losing a good chunk of money this hand is giving him credit for a better hand than you on the flop that he won't lay down and get the hell out of dodge.