Don't beat yourself up over one conversation. He is being disrespectful to your M but I don't think it will help to point it out in the future. They will do what they want to do until they don't want to do it anymore . In the MEANTIME, you are becoming a more fabulous, capable, empowered, self-sufficient, resilient you. For yourself and in an authentic manner beacuse you are taking the time to grow and develop yourself. And if he happens to notice that is an added bonus.
How is he when you maintain contact? Would he interpret it as pursuing if you asked him out? I would not ask out my H now because it would definintely be seen as pursuing. But you know your sitch best. The thing is if you do go out, do NOT fall into the trap of discussing his R with OW. To me that would be a big no-no to be avoided at all costs.
