6-handed 20/40 Live.

Dead cards: K, 3.

3rd: hero brings in with (J3) 3. T at UTG+1, 6:club at MP:, Q at Button call.

4th: hero (J3) 3J and leads, T6 calls, so did 64. Q9 folds.

5th: hero bricks (J3) 3JX and lead again. T65 calls and 64Q call.

6th: I catch (J3) 3J X 6 and lead. T659 raises, 64QX fold and hero calls.

7th: hero brick/checks and villain bets...

Hero doesn't know much about the player except that he is a man about 65. However based on my brief play with him, seem like he doesn't splash around and is competent in Poker. I got three hearts on board on 6th but villain raises anyway! Hero doesn't see two pairs are good enough here, however the pot offers a price about 10.5bb...

What is the range you put T659 on when he raises on 6th? 78, 99, TT?

Villain obviously doesn't think hero has a flush or he wouldn't have raised Six, since he can't beat a flush with his board. With no pair on board, villain could easily think a smaller two pair hand is good and raise to force the third man to fold, or be raising something like a pair plus flush draw and straight draw with 89 or T8 in the hole. If hero never calls the river without a full house then that play is printing money.

Sure, the top of his range is strong, but there's a bunch of other hands in there that Jacks-up beats.

My board is scary and I call his 6th raise quickly. As conservative old timer will villain overplay two pairs by raising on 6th and bet river? Will he bluff river if missing his draw after raising 6th? While considering fold option, am I overusing stereotype here?

This is a clear call IMO. The hearts on your board can actually embolden a bluff because he should know you have to call a 6th street raise and fold the river with a lot of hands.

I have had conservative old-timers go nuts on me, so yeah. You might not be likely to win, but you'll win often enough that it isn't worth trying to finesse the read in this one pot.

Nobody ever got rich from making extra river folds.

maybe should have folded on 6th.

river folds have to be really good decisions.

I don't see how folding two-pair here can be good. Isn't 5th street a check-raise though? It looks like you have either a miracle two-pair or a flush draw... and overwhelmingly a flush draw (especially given the dead-3 on 3rd). If they all check it is not a disaster for your range which is full of flush-draws (and some two-pairs). Always continuing on 5th can't be good, and only continuing with two-pair can't be good so how should we play 5th here?

Looking at 6th, it just seems like you can't fold because aggros will torture you with semi-bluffs and free showdowns.

River you beat nothing but a bluff so it's close. It may even be check-raise bluff territory. I don't think tens-up bets this river ever and you're trying to bluff-out trips, or queens+ up. If your hearts are very live, you can rep a flush perhaps. You'll want his two-pair unblocked so less aces, kings, queens dead helps, and live tens. Might be raise/fold.

What was the 3rd street action? Limp or raise?

I assumed it was completed and called, but not sure re-reading it. I think though this hand is a decent hand to bluff/fold with somewhere along the line, 6th, or 7th depending on blockers. Calling down seems bad. Blockers for his potential straight also lean towards bluff if he possibly has a straight here (willing to play a trashy three-card with a hole in it).

limp

This changes things significantly and you simply should call the river because tens-up could be pushing hard here. Nobody assumes you have anything on 3rd, and nothing more than a pair of jacks on 4th.