Actually two other thoughts.
First, “meanwhile he’d make out with someone at a bar or sleep with a coworker as a one off, that type of thing.” So he could potentially cheat anywhere at any time. Even if he agreed not to go out drinking with the bros, you’d worry.
Second, this: “I do think this is different, he’s older, has probably calmed down & realized what he wants, etc.”. Has HE assured you that all this is true, and told you what he’s learned from past mistakes and that he’s moved on and won’t cheat again? It sounds like you’re trying to read tea leaves here. It’s even more concerning to me if he hasn’t proactively told you why things are different.
Anyway, having a full blown panic attack when your boyfriend goes out is a huge red flag you’re in the wrong relationship.