I'm goign to come back to, and continue, this thought above when I have more time - since I lived int he Austin area, my wife has previously lived in the Dallas area, we have some experience with your climate.
At a high level, I agree with all of the above. I've said the same many times here on BYC. At a more granular level, I can probably offer a few practical suggestions, with significant caveats, of course.
OK, I don't have long to touch further on this - short lunch at work today, and was taking some pictures for one of my threads.
It is very difficult for the typical BYCer to grow, harvest, and store even a substantial portion of what is needed to make a nutritionally complete feed. Even those few that can can't truly compete with the economies of scale enjoyed by the big producers - in both volume and specialization. Being a generalist is great in survival situations, but means nothing will be as productive as potential.
Most of us don't have the equipment, the storage space, the climate, the soils, the acreage, and the geography to do otherwise. The best land is (largely) already used for farming, or has in past decades been converted to small lot subdivisions, leaving the rest of us with marginal soils, hilly, swampy, and/or rocky lands, etc
Dallas has high highs and moderately low lows (as in persistent hard freezes that last more than a few hours), occasional snowfall, periods of drought followed by torrential rains, and areas of clay soils that bake hard like pottery. Not exactly prime pasture.
From experience, corn will grow there, its easy, it will produce relatively densely in relatively small spaces, it requires little specialized equipment, and is pretty easy to dry for storage - if a bit labor intensive. Unfortunately, its also your cheapest bulk ingredient and of no particularly exceptional nutritional value. Its not bad - which is why its used to bulk out feed - its just not good.
TX also has some strains of hard red wheat adapted to the Dallas area. Its high protein for a grain, can also be dried and stored, relatively low in antinutritional factors, but benefits from specialized equipment to harvest and separate. CAN be done by hand, very labor intensive.
Sorghum, and Sorghum/Sudangrass hybrids both do well there. Essentially, a corn substitute in recipes. It has some quirks, but is largely interchangeable w/ corn. Doesn't require a lot of equipment, and I prefer it aesthetically to corn at all times when corn doesn't have full ears ripening. The rest of the plant has a little more value nutritionally than the corn stalks, though it can concentrate some things late season, when your birds will avoid it.
If you have very limited space, would recommend you focus on high value, small area crops which you can spend more time protecting against drought and drowning, and whose prices are much higher on the retail markets. That's clovers and similar legumes to the extent you can get them to take root (some of my soil would, most of my soil would not), "near-grains" like Amaranth which are also aesthetically pleasing to satisfy the HOA, but are relatively low yield - you don't want to be harvesting. Prairie grasses like Bluestem (andropogons gerardii, etc), and low nutrition, dual use herbs you also make use of in your own cooking. Methi (fenugreek), basil, oregano, mints - more for the bugs they attract than for the plants themselves (fenugreek seed is actually high value, but hard to establish).
Might also want to look at lab lab (hyacinth bean) - I'm trying it out in my soils and climate now, we share a lot in common, but not everything/Dallas is 7b/8a, and I'm more like 8b/8a on average - we are about 3/4 of a "grow zone" apart. I also have more sands, more rain, and lower elevation.
My thoughts anyways, running late from lunch, sorry I couldn't add more