I'll offer up a suggestion on how to move to the Master Bedroom. You can always say "wife, I've decided that I am moving back into the Master Bedroom. If you are not happy with my decision, you can either remain in the Master Bedroom or move to the guest bedroom."

If she threatens to file temp orders, call her bluff. What is she going to say? My husband has decided to move back into the Master Bedroom? If I am not mistaken, you are the one paying the bills. They love to make threats. Believe none of what they say and only 50% of what they do.

Try to look at her as a roommate and nothing more. No expectations, but you can be polite and say hello, goodbye, have a nice day, etc. Refrain from any more relationship conversations, i.e, divorce talks and the OM.

Continue to focus on you as best you can. Go out when you need a breath of fresh air or to regain control of your emotions.

Sit quietly, the answers will reveal themselves when you least expect them to.
The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.