I'm not sure my tips would be any good, since mine moved out after a year and a half, but to save MY sanity, I treated him like just another body in the house. I didn't instigate any conversations, thanked him if he brought me anything, stayed in my room or was gone, made food for myself and S17 (D20 when she was home), and if H wanted to eat, fine, if not fine, the kitchen closed when I cleaned up for the night. If H left a dirty pan, I washed it and hid it for my own use, but not his. He oddly learned to clean up after himself.
Take care of yourself. Do things your way in your timeline. If your MLCER is in your way, figuratively or physically, side step and keep doing it your own way for you and your kids. It sounds trite, but continue forward as if he is not coming back and is just some guy who lives there. Pay the bills that affect you and your kids, let him sort his own mail and paperwork. Put money in an account of your own. $20 at a time if you need to.
I also colored. A lot. And drove off road. So hobbies are your friend.