Onmyown You're assuming people have the same moral compass as you or that they know the truth.
The OW parents - They may hate him. They may think he's a fucking prick but are worried if they boot him out she goes too. They may think he's great because he's lied and manipulated his way into their affections.
He most likely has told them that you've got soneone else / kicked him out / it's amicable - that sort of thing. they won't know the actual truth. They may have swallowed his victim act which inevitably paints you in a terrible light. Who knows.
What I became much better at was being very clear about who was worthy of my time and energy. When I was left with a small baby in circumstances that would have me as a guest on Jeremy Kyle - there were people who helped me and people who hindered. People who pretended to care but just wanted to know the salacious details. Cut out people who hinder from your life, from your thoughts and from your future.
The best and quickest way to get over this is to change what you spend your time thinking about. Change your thoughts and you will change your life, your feelings and your future. Every time your thoughts wander to OW etc bring them back to your DCs, to survival, to friends etc. don't let these twats occupy your mind.
Don't be distracted by the OW and her family. For whatever reason they have behaved reprehensible towards you and your DCs. But that's a matter for them. They are not worthy of your time.
Your H took your son's money - I am appalled.
He is a fucking scum shit head. Your poor DCs, that must feel so disappointed and so ashamed. Get angry for them. Anger can be motivating and empowering.
They will feel so proud of you for getting shot of him.
You are getting stronger every day. You already sound like a different woman to the one who started this thread.