Ryegrass is not going to add nutrients to the soil. It is fine for holding the world together and providing some forage, but it most certainly will suck the soil dry of moisture at a time you want your coastal to come back. By all means, use some clover (Burleson Co. is a soil nightmare, so be sure your clover matches the pH), and a mix of forbs (tillage radish, forage brassica, etc..) and grass such as oats (gets out of the way earlier in the season). You have a fairly narrow window closing in with day length and weather, so get it in pretty quickly. Yes, clover needs fertilizer (a sniff of N and lots of P and K depending on the soil) and when mixing with other forages extra N may be needed.
On a side note, I doubt your coastal is toast in those spots. Wait until spring and some rain to decide about replanting. It may well be that fertilizer and management will fill your voids. Go talk to Veronica at the NRCS office in Caldwell and tell her that her old agronomist sent you.
Being in TexAgs jail changes a man……..no, not really