Hang in there Tim! There is ALWAYS drama in the family. I don't know if you are anywhere close to getting your own transportation, but that would help a lot. Despite her being your Mother, you really don't need that hanging over your head holding you up dealing with issues.
Regarding the Ex, well...no great advice there. I've heard horror stories.
Find something positive you and the wife and focus on. And spend as much time doing that as possible. And if that positive is the kids, that will make it even better. I myself love kids, but I'm a bit of an old school Dad. I'm their friend until they disobey.