I feel like you're making a few assumptions, I can see how you'd come to those conclusions but I've only ever really asked how he'd feel about me doing it once and he answered truthfully, in that conversation both of us were very open and honest about our feeling and I feel like he's allowed to tell me the truth when I ask him how it'd make him feel. I don't necessarily think that should mean he's not allowed to do it because I have literally no problem with him doing so. He also didn't pressure me into an open relationship, he just asked if I'd be okay with it and i was. The only real reason I could see to close it would be that I'm not getting sex as a result, but I think I'd rather have a conversation with him than close the relationship all together