After reading what you just wrote MHO is that you should not worry about the OW. That R is not going to last. Your H at some point is going to realize that OW is mentally ill. Then he will be running looking for another fix.
Think about that and understand this is why you have to detach and go on living your life as if he is not coming back but make your self the best option. Either for him or for someone else. YOU deserve that!
This is not going to get fixed fast. You can do this.
