You really should consult a family lawyer in person about this. First, $5500 in arrears in child support is really quite a large sum. You can hire a lawyer to chase that for you. You could also contact the Texas Attorney General's child support enforcement office in your area and complain to them. They have been chasing down non paying parents for many years. But, the morality clause you need to discuss with a family lawyer who can look at it and the entire divorce decree. Generally speaking, you can file a motion to modilfy the clause. Maybe granted, maybe not. Maybe even agreed to. Speak with a family lawyer about the details of your situation and for advice on how to proceed.
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The morality clause needs to be reviewed by an attorney to determine the scope. Normally remarriage by a former spouse would not violate a morality clause. Morality clauses are normally use to prevent a spouse from living with an unrelated individual with whom they have an intimate relationship.