Ok, alittle focus on OW for a moment. I think she is very envious of you. I believe she wants to take your place in everyone's eyes. The problem is she can't accomplish this unless she has your participation by giving her your spot. DON'T!!!!!!! Maintain all relationships that you can, I would even try to make them better. If you can do that, OW will panic and turn up the heat on your H, which we know he doesn't like. Don't allow grief to paralyze you. Fight for your marriage. If you were not married to H and you wanted him, how would you get his attention without pursuing? You know him better than she dies, use that to your advantage.
Secondly, has there been anything in your life that you wanted to do but couldn't because you were married? Compile a short list and start doing those things. This will help get your focus off him and on you.