I'm not certain I have advice. BUT I can relate.
Living with mixed family and having all the kids be adults is not easy.
Currently I now live with my mom, her boyfriend, his son and sons girlfriend, and my two brothers. We have 4 vehicles between us. EVERYTHING is stress in one way or another.
One person doesn't do enough around the house, one person didn't flush, one person doesn't let the dogs out, one person does this or that, its tiring.
There is always at least one person too, that cannot stand the things someone or anyone does. Doesn't matter how stupid or little it is, they can't handle it. (or in our case, random war over insignificant pet peevs)
Unless your children are the type that are happy to be living off mom and dad it's not easy for them either.
I feel like I'm constantly the mediator/therapist here. There are the.."tense" feelings between different sides of the household. But i generally live under the idea that we ALL live here, we ALL have to live her for the moment and do my best to remember everyone lives differently, and accommodate that as much as possible. You would never kick one of his kids out, so it should be the same in return yes?
try some counseling between the two of you. living situations like that can eat at everyone involved, and even the tiniest thing at the wrong moment will cause someone to spaz, its necessary for everyone to know how to properly deal and get over that. (and i wont even get into the wars we have