Yes, please report him.
If he really had an epiphany while in jail he would have never contacted you. My guess is the email from the MIL was a transcript of what he told her to write to you. Didn't like the response, so onto button #2 "I've had an epiphany". They just keep on until they push the right button.
Please be safe, and stay strong. You are doing so well with all this. I hope you will follow Lexie's advice.