I think 3bet pre is fine, because AJo isn't going to play particularly well OOP in a 3-way pot but it has good blockers. However, I think your 3bet sizing is way too small. This would be a good sizing for a 3bet in a heads-up pot in position, but it's much too small here. Generally as a squeeze I would go something around 3x IP and 3.5x OOP, so a good sizing here would be around 1000-1100.

The reason for this is that the first player in these spots, the OR, is almost always going to be aware that if he calls, the guy behind him is getting great odds and will probably also call, so when you're this deep-stacked, if you make it small like this, the OR is very rarely going to fold. You need to make it bigger so that you can at least get heads-up vs the button, or take it down preflop entirely. Going to a flop OOP vs two villains is the worst outcome here.

Postflop, however, I actually really like your line. Cbet is very standard, c/c turn is good with our heart draw, and on the river it's really tough to put anything in his range that we actually beat, so I think I like the fold. Apart from the 3bet sizing, nice hand. 🙂