Revoking your parental rights releases you from future child support claims, but not past. That is up to the judge and depends on other factors, such as whether she has ever been on welfare. If she has, she has no legal right to have the arrearage set aside. The money belongs to welfare and will continue to collect interest until it is paid.
The interest rate will be from 3% to 10% per month. I’m not sure what the Texas rate is.
Check with Texas Fathers for Equal Rights at https://fathers4kids.com/. And no, once this is done, it is permanent. You are no longer the father.
But, since you are out of the country, you haven’t been a father to them anyway, due to lack of contact, and not paying your child support.