This is beyond sad. As I recall there are at least two kids and a newly bought house in the picture here. It flops from "we went to the courthouse together" to stolen food and money.
I see this as coing to a real head at some point, some how. Not sure if OP or the wife earns more (isnt the wife a clerk at mcdonalds?), but one has to make a basis in terms of stability, earning power, and related areas.
If I were OP, I'd have called the police for robbery if all of the food in the house was gone when I got home. Sounds like he is divorced now, so there are two private parties. IMO the approach now is to enable the perception of stability on his side (and Im assuming that he is more stable, a higher earner, and more caring than she is with her own temper), and that she has real and legally documented issues.
I doubt that OP and his ex have more than a pot, probably not much of real value. So the key thing here is two children who need a stable life and to not be messed up like so many kids who had divorced parents at some point in their life. OP, you shot "hot bullets", as a result you have two kids, you need to do what is best for them first and foremost, regardless of what it is.