I think this is a really good spot for a 3-barrel, yes. Let’s look at it step-by-step:

Flop: You have a gutshot, backdoor flush draw and two overcards to second pair. This is a good c-betting hand in any situation, especially against a big blind who is probably defending at least somewhat wide, perhaps very wide.

Turn: You pick up equity with an open-ender – it’s not the nuts as far as two-barrel cards go, but if you bet here then there are a lot of good river cards for you, where you can either win or bluff. You block the nuts (T9) and if a T should roll off on the river then you have a great chance of getting paid off nicely by a 9x hand that made a T high straight when you make the Q high straight.

River: Villain’s check-calling range for two streets includes almost no strong hands. There are enough draws out there and bad river cards that the villain would likely raise any set or two pair on an earlier street, so the only two pair or better hands you have to worry about are A6/A8, maybe A7 if villain is really passive and calls all Ace high on flop. There are some Queen-x hands that might hero you down, but there are also plenty of hands like 56/97/T9/98 that will find it very difficult to call a river bet.

As far as what you’re representing for value, let’s see…QQ, 66, 88, 77, AA, T9, 87s, AQ, maybe 86s, maybe 67s, maybe even 54s. That’s probably close to 40 combos of hands there, depending on how wide your opening range is. I think this is part of what makes it a great bluff spot.