Preflop
From such an early position I would look to use a fold or 3-bet strategy. The issue with calling is, you open the door for everyone behind to squeeze. Maybe you are a little protected, if everyone perceive this player as very tight, but if he is very tight, why do you even want to get involved with him? I dont want to 3-bet this hand against someone with a perceived tight range, so I would just fold.
Flop
SB came along for the ride as well, you flopped a gutshot with two overs, and now the preflop raiser bets full pot. If he is that kind of nitty player, which you say, then this scream overpair or even set betting "for protection" on the wet board. You are not getting good
odds to draw to just a gutshot, 7h could spell trouble for you, and you also still have SB left to act. He has just naturally checked to the preflop raiser, so he might have flopped a set or big combodraw, that he wants to check-raise. So once again I would just fold.
Turn
Other than a 7 this was the best card in the deck for you, because you picked up 4 additional straight outs. When he check, I would also bet. Even though his hand looks like an overpair, maybe he could still have some AK or AQ, that was taking a stab on the flop and shuts down, because he got both players to call. And you obviously want him to fold that. You also want SB to fold, whatever he is still hanging on with.
River
I am not a huge fan of this bluff. As you say yourself, it is a tall order to ask someone to lay down an overpair, which is probably still a large part of his range given the preflop and flop sizing
tells. I also think, you have a little bit of showdown value, since he could perhaps have
hands like AK/AQ/KQ of hearts, that take this line, and you beat those hands now, since you rivered a pair. I also think, spades coming in is less scary for him than hearts coming in, because for you to have spades, it would need to be pretty much 8X or 6X exactly. And finally I dont think, your blockers are important, because he probably dont open QT and certainly not T7 anyway. It would be more important to block spades, which you dont. So I would just check back and take my small chance of winning at showdown.
Conclusion
To me this whole hand is a little FPS (fancy play syndrome) to be honest with you, and I think, if you want to play like this, 6-max might suit you better. At full ring I think, you will end up with a result like this a little bit to often for this to be long term profitable.