Luv1589 - One very important thing that I learned here and it may sound like tough words to you but you may need to hear them. Your old marriage is over. It has been broken into pieces. You are still holding many of the pieces but probably have no idea if H is holding any.
You can use those pieces and new ones that he will have to make and ones that you make together to build a new MR on the ashes of the old, but it will take commitment and hard work.
It seems that at present that H has no interest in doing his part. You can't build the whole thing yourself but you can build yourself. Making yourself stronger for you and your family is your first priority right now.
It's buried in some of the reading you've been assigned as "homework" but most people here feel that it is necessary for your H to feel the "loss". The loss of your MR and the loss of you. Presuming you aren't OK with being his having a third person in your M then you need to make that abundantly clear to him. If he can't decide between you and OW then perhaps he needs to go into a neutral corner until he does know. You're not rejecting him, you are giving him space to find himself and complete his own journey. You can create that "loss" by "detaching" - by withdrawing those things that you as a loving wife have been providing to him. You can still treat him with courtesy and respect but if he's not going to be a H to you, you need to try to stop being a W (if it's cookies let us know - doodler and I both love cookies as does darknes - double-chocolate for him I believe). Going dark is a bit farther along that path. It shows that you have moved on with your life and don't need him any more and you don't need him to see your light but you can still let that light shine brightly.
Speaking of light, some of the reading you've been assigned as well includes the "lighthouse" story which is personally an inspiration for me on my own journey. I tend to tell jokes when I'm under stress or nervous so it should be no surprise when I also mention the version of that which I read which was titled "be a lighthouse and not a tugboat".
Good luck - this is going to take a lot of work.
Sending you good thoughts.
On BD H52, W50 T27, M26 S21, D23 BD-9-Mar-16 D-15-Jan-18 Final-19-Apr-18 I am a storyteller. The story may do you no good. But a story is never for the listener. It is always for the one who tells