Idk what to do I know its a complex situation but I wouldnt react this way if I didnt feel threatened. Hes talked to other women in the past and it hasn't effected me except for his ex while they were breaking g up he pushing boundaries with it but they were more set for him so he could heal but its a mess.
Hello and welcome to the family. I'm so sorry you're in this position and the harm its caused you. However, I don't feel like it's a complex situation at all.
He's responsible for himself. You're responsible for you. Those are two different things and you must think about them separately.
First, let's talk about him. You entered a relationship where you're being unfaithful to your husband, so you gave him permission to be unfaithful as well. For a BPD, that's a "best of both worlds" scenario because they get all the feel-good emotion and excitement without an ounce of actual comittment. By definition, that's not a relationship...its an arrangement.
However, he's not abiding by the arrangement since it sounds like the "best of both worlds" isn't enough for him. He wants even more, he wants full control and submission, which is more of an NPD trait. BPD/NPD are on the same spectrum and often cross paths. Maybe he's just trying to make you jealous. Maybe he genuinely expects you to be excited about how much he's into his boss. Either way, it's manipulation and it's cruel.
Now let's talk about you. You're responsible for you and only you. You're married to one man, and in an arrangement with the other. You also mentioned that you're happy with your husband, but you made a statement that if you handled the past different, maybe you never would have broken up with the other guy. There's a lot of confusion for me there, and I'm guessing there's a lot of confusion for you too.
Which relationship takes priority? The one that you said was "good" or the one that brings "anxiety, jealousy, and disrespect"?
It's essential for you to make a choice here. Keep doing what you're doing until it all blows up spectacularly. That's what the "best of both worlds" always brings in every circumstance- you can't find one instance in the history of the world where 4 or 5 people lived happily ever after in this circumstance. It always breaks and everyone ends up hurt.
Or you can create healthy boundaries where you stop accepting the abusive behavior. I think either path leads to the same outcome, unless you're willing to leave your husband and marry your long-lost love under these abusive circumstances. But you also said that you're not even his favorite person right now, which is another cause for serious alarm.
Nobody here can tell you what to do, but I'd suggest you really think about which relationship should be your priority right now. One is good, one is bad, and the bad one will always go in circular patterns like this because serious mental illness is at its core. BPDs are terrified of someone leaving them, yet you're leaving him every time to go home to your husband. That alone will keep him unstable and guarantee selfish behavior.