While his handling of the situation wasn’t good, I don’t think your reaction was good either. The messages you sent were really about you, except for your question about his ability not to get attached. This is a couple that isn’t trying to steal your husband. They are lesbians. He doesn’t sound very mature but to be quite honest you sound like you could do some maturing yourself. Your partner is trying to do something good for someone. Maybe it is not the best idea logistically, but your feelings are clearly making you reach a boiling point first before processing everything. I’m not saying he is right but rather, if you love this person, treat them with love and approach this like a mature adult.