I second visiting a lawyer (or two) if you haven't already, to figure out the best way to deal with custody.

In my state, for example, physical and the other part of custody is granted 50% to each parent as the norm.

Also, in my state, there's no ability to legally separate.

And, in my state, the parent that leaves the martial home is considered to have abandoned the family, which obviously isn't a positive thing.

I also hope that you get a chance to really work through your finances before you implement Plan B. I'd just hate to see you and your kids suffer with basic needs being met.