I am very sorry that the drama continues. I'm glad the chemo is continuing to work for you and it sounds like you are doing well w/it except for being tired. Some of that tiredness is from the drama you are receiving nonstop from your xh.
As for the threats of calling the police if you deny him visitations...let him call them. Are you documenting everything, especially the number of visitations? If not, begin to do so. He's a big bully who has no control over h is life w/the new wife and he's taking it all out on you. Don't engage w/him any more than you have to. If the conversations start to get ugly, hang up the phone. If the emails come in, don't respond right away. Only address issues that you need address in a calm tone (which I'm sure you are doing).
As for his job...what happened? Was he fired or did he quit? Could this be a ploy to lower child and spousal support to you? If he's now harping on seeing the kids, then he's got money to visit w/them and do things w/them.
As for your former MIL, she's no better than he is. Please stop reading their facebook pages as it's not doing you any good. "Little" people have to brag about their happiness all of the time, which to me, is proof that it's not all unicorns and pixies over there. You know what you had for 22 years and no matter how much they try to rewrite history, people who knew you, know what you had. They are just trying to convince the world and themselves that they did the right thing.
As AJ pointed, do your homework...there are organizations that can assist you. You aren't well enough yet to get a job and you don't want to set your recovery back by trying to work right now.
I will continue to keep you and your children in my prayers.
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.