I'm totally playing devil's advocate here, but are you close to his mother? Is there a reason for you to go outside of your role as his partner? I know the fact it's the possible death of your children's grandmother makes things dicy... But I'm just thinking about how he is doing all this awful stuff to you, yet you are being expected to show up for the family emergency, support him, and play "wife" like nothing is wrong. He fired you as his F. He is sleeping with other women...but you still have to go help pick up the broken pieces for him and his family?
If it weren't for the fact it's your children's grandmother, I would say leave him to deal with the consequences of a life without you... But I know things are complicated.
