Bluff that worked, but should I of made it?

[trumpman84]

I'm just trying to pick up a few plays that vary from my normal ABC poker...what do you think of this one...spewing?

No specific reads on villain, but the table has been pretty loose, but not particularly aggressive or passive but more towards the aggressive side.

.50/1.00

UTG limps, I raise from MP to $4 with 9 [img]/images/graemlins/diamond.gif[/img]9 [img]/images/graemlins/club.gif[/img]. SB (Villain) calls. UTG calls.

Flop is J [img]/images/graemlins/diamond.gif[/img]4 [img]/images/graemlins/club.gif[/img]6 [img]/images/graemlins/diamond.gif[/img]
Pot is $12
SB leads for $3. UTG calls. Getting 6-1 with the possibility of my hand still being good, I decide to peel one and see what develops on the turn.

Pot is $20 after rake.

Turn is a K [img]/images/graemlins/spade.gif[/img].
SB checks, UTG checks. I feel UTG is weak and I think SB just has a jack, so I decide to represent AK and bet $12. SB is stubborn and won't go away..he calls, and UTG folds.

Heads up to the river, pot is $43. River pairs the board, a 6 [img]/images/graemlins/spade.gif[/img].

SB leads for $10. I read this bet as a blocking bet and I want to raise it, but my head keeps telling me not to bluff bad players. I really think he has just a jack, probably AJ, so I can't just call. I feel the pot is big enough to justify a bluff, so I raise to $40 and put him to the test. He has $60 left after the river bet and I have $20 left after raising.

Good bluff or chip spewage in the long run?