the problem is probably the priority of the liens. The mortgage company most probably has a superior lien to your child support arrearages. It sounds like CSE is doing what they can, although with three contempts (one criminal) and still $55,000+ arrears it doesn't sound like the purges were very high. If he is vacationing in Mexico (with a suspended passport?), it sounds like you need to hire a private family law attorney to possibly take over for the DOR. I do not recommend your trying this on your own based on the facts you gave. Realize though that you are going to have a rather large retainer to pay to hire a private attorney for the issues described so that is something to consider as well.
Family law rules differ significantly in every state, especially procedural rules. Always seek the advice of an attorney in the state where your divorce was filed.