Hi Roxanne,
wow that must be so hard, but yes staying calm is key.

Are the children currently residing with you? In the UK we look at how settled the children are and if moving would be a needless disruption (I am a social worker). The welfare of the children are paramount and here the needs of the parents not.
Not knowing the legalities or principles where you are I can not comment on possible outcomes but I would have thought that where they are now currently settled would have some bearing.
I hope it goes well for you and your children.

Yes they live with me sunday night at 6pm till friday night at 6pm and see their day friday at 6pm till sunday at 6pm. There is also domestic violence involved, my STBX was arrested for spousal abuse last november, I am hoping that has alot of way in this case. I don't want to have my kids uprooted from their school and friends and moved away from me. Thanks for your advice. I am just afraid he makes so much money that they will only consider how he is able to afford them and I am not.

I can say that in most cases where there is domestic abuse it will out way any financial gain!
Removing children from a stable home environment because of money is unethical by any means.

Hopefully you will be fine.
Are the children of an age to voice their opinion? That should also be taken into consideration.