1. "I put him mainly on steals" is not an answer to "why'd you 3bet?". I'd check back flop because only sets and AsKs will continue most likely and maybe KQs which is very unlikely.

2. As a preference, I always bet these Axx boards in 3bet pots like half pot. River is kind of gross. I wonder if you have seen him minraise preflop before? I don't think you can go too wrong with calling or folding. It's hard to see a worse PP play it like this but I'd need actual reads, not just stats.

3. You have to know his 3-bet tendencies. At a lot of stakes vs. 6% 3bettors they don't have just a value 3-betting range meaning they 3-bet say JJ+/AQ+ but also lower SC type stuff. I think you played it pretty well overall because I really cannot see him having a worse hand unless it's A7. Obv. if you know he's aggressive he could be doing this with a lot of draws which makes his line pretty good because he can buy a cheap river card which also allows for FE.