Support is modifiable based upon a material change of circumstance.
There is no way to deny the court the ability to modify an order if the facts support a change. Be sure to get you visitation order situated before leaving the state because that too can be troubeling ot deal with after you heva gone. I can't tell you what support would be if she were to marry because I do not know what he makes or what deductions would be on theri joint return. His income will impact her tax burden.