Trying out bluffing OOP vs nit

So yeah I am working on my play OOP and bluffs.. Not the best combo but I have to learn.
I played this hand vs a pretty tight nit 54 hands 12/10 3b 6

PokerStars - $0.05 NL (6 max) - Holdem - 6 players
Hand converted by PokerTracker 4

MP: 103.6 BB
CO: 91.8 BB
BTN: 105.6 BB
Hero (SB): 100.4 BB
BB: 101.4 BB
UTG: 149 BB

Hero posts SB 0.4 BB, BB posts BB 1 BB

Pre Flop: (pot: 1.4 BB) Hero has A♥ 3♣

fold, fold, fold, fold, Hero raises to 3 BB, BB calls 2 BB

Flop: (6 BB, 2 players) 4♥ 3♥ 9♣
Hero bets 3 BB, BB calls 3 BB With the A♥: and par 3 I want to Cbet here. Occasionally x/R for protection? Is is protection?

Turn: (12 BB, 2 players) 5♣
Hero bets 9 BB, BB calls 9 BB Making a large bet.. Maybe even better to overbet here?

River: (30 BB, 2 players) 7♥
Hero bets 27 BB, fold I my mind I had 2 options x/f or potsize bet representing a flush/straight here.

I am definitely not comfortable if I see my ranges after I played these hands. BB vs SB. A lot of cards hit here with possible flush draws / straight draws. also, small pocket pairs making a set here.

Though decision here. Hope I can find some answers from you.