Your mom may be creating potential gift tax exposure, or at a minimum triggering a reporting requirement, if she gives each of you a huge lump sum of money. She may want to restructure her gift in a series of annual sums that don't exceed the annual gift tax exclusion ($12,000).
If she has not yet made a gift of the money and your ex- is being a jerk, she can reconsider if she wants to give him anything.
If you and your husband cannot agree on how marital debts should be divided, you'll end up having to litigate the issue. If you're not yet represented in the divorce, consult a lawyer. If you are, talk to your lawyer.

