If he's limp/folding a lot I would even raise 5x preflop at NL5.
On the flop ok cbetting 4value, but the size is to small. Here you are against a random and you're betting 4value, then bet BIG. You can even go as big as close to pot since he's not folding Kx, Tx and probably neither 9x. Of course he's calling w/ draws so Qx, Jx (given he's an unknown fish). I'm never betting lower than 3/4 of the pot: I don't need deception and my FE is just slightly influenced by the size, so just get all the value you can get.
The same is valid for the turn. It's highly probable that you have the best hand. You don't know nothing about his f2cbet or his turn bluffing frequency. You don't want to give him free cards and ofcourse you want to get value from your hand, so just send the 2nd barrell (again 3/4 pot). You're getting some weak hands to fold, but there are now some extra draws on the board and he's a fish so most of the times keeps calling w/ a lot of pairs.
On the river... I'm not understanding what's your plan.
Now what? Is this a good spot for an overbet bluff?
Bluff? Why do you want to bluff? First you have TPTK which is, given oppo and given the action, a pretty decent hand to get to the SD. Second, do you really think a fish is folding set to an overbet here? You would just be throwing money at him: don't overthink, it's really unnecessary at these limits.
Given his play, a set is a good possibility.
Why? Admitting he's raising only TT+, he can only have a 9 set, since he's probably folding both 77-88 on the flop, and also he's probably checking back 88 on the turn.
You're playing result oriented, and you're overthinking too 
Just keep things "clear" and everything becomes much easier
