I would immediately take a certified copy of your current court order to an experienced family law attorney in your county.
You need to talk to an attorney and see if you are restricted to the county that you currently live in.
Technically only the child can be restricted to a specific county and/or counties.
You, as the primary parent, are free to live anywhere.
Only the child is restricted where the child can live.
If the child is thriving then why should the child's life be disrupted because you are getting married? If the child has friends, family and is established in this area, then why should the child's life be turned "upside down" and be moved? Why should the child's life be totally changed because you want to get married? If the child is in school, then why should the child be moved away from the life that the child knows?
If the other parent is very active in the child's life, the other parent can object to you moving the child.
In the State of Texas, many judges will not allow the child to be moved away from the other parent just because one of the parents is re-marrying.
The other parent can ask the court to allow that parent to become the primary parent and then you would be ordered to pay child support and you would then visit the child.
If the other parent is an absentee parent, the the judge would probably allow you and the child to move. You need to talk to an attorney about the defination of an absentee parent.
So before you set a wedding date, I would set an appointment with an experienced family law attorney in your county!
Often the other parent will allow you to move away if you are willing to negotiate -- such as (1) reduce child support to a token amount (2) you pay all costs of transportation for the additional costs of visitation (3) you give the other parent expanded visitation to make up for moving so far away - such as every Spring break, all summer and every Christmas (4) buying the child and the other parent high-tech computers so that they can keep in touch via the internet.
I always suggest mediation rather than litigation.
True Story: One mother remarried and moved the 3 teen-age kids to Hawaii. A judge in Harris County made the children move back to Houston to live with their Dad.