Be aware that there is on-going construction on I-35W on the north side of Ft Worth and around the I-35W/US 287 interchange. I think it only involves a relative short distance along that route. Maybe someone who lives in Ft Worth or has been thru there recently can give an update.
You will not have a problem finding fuel on US 287. There are many towns along the way, especially between Wichita Falls and Amarillo, and most all have at least one station that provides easy access for a large RV whether MH or long truck/trailer. Just start looking before the tank gets too low. A very good highway all the way to Amarillo.
As far as RV parks, there are some south of Wichita Falls (between there and Decatur) but I have never stayed at any of them. I don't remember many between Wichita Falls and Amarillo though. We travel that route every year but for us Amarillo is our first stop.