Oh it's hard to break free! The tentacles of my guilt run through my life-- "I failed to make it work" "I'm putting my kids through something they don't need to deal with" "I'm a bad mother!" ... .all those words run through my head.
Ouch. That's an awful lot of guilt Elpis. I'm sorry he's putting you through this.
My Achilles' heel is my children. I can relate.
My ex would criticize my parenting. It hurt when she said I was an awful uncaring dad. She would would erupt with disproportionate anger while I was trying to serve supper to the kids saying foul language in front of the kids. It hurt.
I'd tell her to not speak to me as such in front of the kids and she would continue this behavior. A boundary is if you do X I respond with Y. What are your boundaries when he communicates in this manner now? My ex guilts me every so often with the kids. What helped me is that my head cleared and I'm detached and emotionally detached from her words. It's not triggering and she may send something once and it remains there ( 1 email ) She knows by now that she won't get a response from me. She called me a wall once

It starts and ends there is my point.
You are correct you are a good mom and have a big Don't let his opinions define you.