Villain is a reg

How often do you think he'd raise you on the flop with flopped flushes?

How often do you think he'd bluff turns/rivers with pairs that he floats on the flop (like 7d7x)?

Do you think he'd use larger sizings with other value combos? 66/44/A4s/XXdd etc.

Do you think he ever v-bets something like AQ?

I'd imagine his only natural bluffs are hands like 78s and pocket pairs with a diamond. If you don't think he ever turns something like 7d7x into a bluff then I'd just pure fold. He probably doesn't have any/many off suit broadways with a diamond that call pre, call flop and bluff turns/rivers as QJo/JTo probably fold pre, hands like KQo/KJo turn a pair, etc.

So, mostly depends on the second question imo. He still has lots of natural value combos and many potential flushes: AK, A6s, A4s, XXdd, 66, 44.

I don't think you're supposed to 3bet pf especially this deep.