It's somewhat troubling that your boyfriend can see that this upsets you, yet he persists in this behavior. It's also weird and immature that he's decided he likes having this out of state guy under his thumb. That just seems icky to me. Does he think that way about you, say such things about you?
Also, whose idea was it to have an open relationship? They can work, but they're not for everyone. If you were pressured into it, and now you're having buyer's remorse, you might want to rethink your entire relationship, and not just the open aspect of it. If this guy can't give you what you need, without you having to make a concession that you don't truly believe in, well, you might want to think about what that means.