Don't do it, don't contact her or him. It won't feel as good as you think it will when you are done and yes, it could cause some serious problems. Probably not with custody issues, but H could really backlash and be more angry with you. YOU are the better person, YOU are above giving them the time of day. YOU are carrying on and living a morally sound life. Do not get involved.
HUGS!!!
I am scared to make a list because I feel the cons would take up pages and I would be stuck on the pros, like you.