Well, its hard to put your opponent on a particular hand, since there are so many draws there and also, cards on the board that can very possibly make a pair. He could just as easily have a straight or a flush draw as a made hand.
YOu are right about the betting pattern being strange though, because when someones got the J or even the 9, i would expect a checkraise rather than a weak liead, and as i have said alot of times, i have no respect for the weak lead, and i am more inclined to raise the flop and lead the turn if someone does that.
The weak lead, to me, is often used as a way to find out where your at when you have a really shitty hand for cheap, and/or take down the pot on a semibluff at minimal cost (a CR being the costliy way to try and do that) Most people dont have the cajones to CR/lead the turn with something like
here- but if you wanna mize a pot, then thats how you should do it IMHO.
By the way the hand shookdown in the end, i am going to give him credit for either (a) a busted diamond draw or (b) QT, and you lost on the river when the 8 got there. If he is a real douchenozzle, he might play a 9 like this, but i doubt it. I say- one of two draws, either the one that got there or the one that didnt.
If he had 8T or a diamond draw that ended up making a shitty pair on the end, my guess is that he'd check it instead of value betting on the end. THat bet on the end is one of two things probably, either a big hand (presumably one that just got there) or a busted draw.
I am seriously going to feel retarded if he had something stupid and obvious like JQ by the way, which is probably what he had.