Your best option is to hire a family law attorney. It sounds like you need a "motion to enforce" rather than a "show cause." You may be able to find forms on the State Bar of Texas website or your local courthouse. Good luck.
This is important stuff. Better to just hire a family law attorney to do it right. If you insist on doing a DIY project with this, start with your local public library. If that does not work for you, you can try the SMU law library.
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I agree with Attorney Giardino but want to expand on that answer.
Texas doesn't have show cause forms to make a party show why they're disobeying orders. Instead, we have motions to enforce court orders. These are ways to let the court know someone is disobeying their order and they need to hold that party in contempt of court. Holding someone in contempt can come with fines, jailtime, license suspension or payment of attorney fees (which is why some attorneys will take these cheaply).
Instead of doing it yourself, I'd consult a local attorney.
Fortunately, the State of Texas Attorney General's office takes nonpayment of child support very seriously, and launched an extremely effective enforcement program. Here is the AG's description of that effort: https://www.oag.state.tx.us/alerts/alerts_view.php?id=149&type=3
You may want to contact the Texas Attorney General's office and work through their system (FREE OF CHARGE TO YOU) to collect the funds not paid to you. This won't help you with the nonpayment of debts assigned to him in the divorce decree, but will address collection of past-due sums on support.
As to failure to pay the debts, I first suggest that you contact the creditors involved, provide them with a copy of the divorce decree or other order obligating your former husband to pay the debt, and attempt to obtain written assurance from them that they will not look to you for payment. If they do anyway, and if you do not have the means to pay the sums owed, document that by sending the creditor(s) a writing explaining this in detail. Then, in the event an account is turned for collection, contact the three credit reporting agencies and advise them in writing of the court-ordered payment of the indebtedness by your ex-husband and his failure to abide by the court order. This will help protect you from any adverse action that will be taken against your FICO score if the court-ordered debt and its nonpayment otherwise went unreported.