Here's some thoughts from my experience and perspective.
Self sufficiency is doable, but it depends upon your definition. It's been argued that self sufficiency is being able to meet all your own basic needs without outside help. BUT what if I sell my excess vegetables for cash, then use that money to buy a tractor and gasoline? Is using a tractor being self sufficient? Or using that money to hire someone to install livestock fencing? Some argue that it's not. Sigh.....to each their own ideas. In my own mind I've decided that using the money my farm earns and spending it on the things I need is indeed my being self sufficient. Based upon this definition, I'd say the self sufficiency is very doable.
Could I be self sufficient on 12.5 acres in Texas? Perhaps, but I have no experience in Texas, so I can't be certain. But I have learned that I can be almost self sufficient on 20 acres in Hawaii where I can grow food year around, access additional food via hunting/foraging/trading, and have much reduced energy needs.
Let's look at food. As long as you have access to water, fresh organic green material to make compost (your source of fertilizer), and knowledge of how to grow it, your 12.5 acres should be able to produce all your own food. But I surely wouldn't turn my back on hunting, foraging, and trading. No one piece of property can provide all the dietary variety we have come to expect for our good health. Nor would I strictly adhere to the 100% goal, because life gets really boring and frustrating without the spices, salt, coffee, chocolate, and non-acclimated foods one enjoys. For example, I can't grow most nuts and stone fruits where I live, so I do buy things like walnuts and peaches with my farm income. Remember, that's still being self sufficient as far as I'm concerned when I sell my pumpkins and beans to buy peaches......or when I trade peas and cabbages for cow's milk. One thing I don't grow is much in the way of grains. So I trade for homemade breads.
Speaking of milk, do you need several gallons of milk a day? Cows can give a lot of milk, so unless you know that you can sell your excess or feed it to a pig (even a pig would be hardpressed to consume the milk from two cows a day), having two dairy cows may not be your best solution. Even with my 20 acres and not having to feed cows during dead winter, cows don't make sense for me. Thus I trade for the cow's milk that I want. And I keep 2 dwarf goat does (and a buck who resides on a back pasture away from the does) for fresh milk. It's a lot less daily work, less pasture needed. And keep in mind that a bull is needed somewhere along the line for your cow to produce milk. Why feed a bull when you only need him for a day or two each year? It's too expensive to maintain a bull year around for one or two cows, and it's also very dangerous. Bulls can be problematic. Besides, as pointed out, cows require a lot of feed, so unless your 12.5 acres is currently lush pasture, you've got a problem to start with. And getting them through the winter will require purchased feed. Skimp on the feed and you'll lose your milk supply.
Chickens - always a good small homestead animal. Your breed choices are fine. 6 hens and one rooster is usually enough unless you're using them to process compost and supply fertilizer. I maintain 50-60 chickens for eggs (they are good for trading), our meat, and to provide fertilizer, and process our garden and donated waste foods. That's most likely far too many chickens for most people, but it works fine for my situation.
Rabbits - another good easy homestead animal. Good for meat, selling some babies as pets, providing fertilizer. If you learn to tan your own pelts, then the pelts are a plus.
Ducks - If you like eating duck, then they are fine. Muscovys don't need a pond and are far less messy and quieter. They give a decent amount of eggs and a decent meat return.
Sheep - good small acreage livestock. Can provide milk for cheese or cooking. They don't give much milk at a milking, but the milk freezes well. I stockpile mine until I want to make cheese. They provide meat. I find that some breeds taste far better than others. Plus we harvest our lambs very young (40 lbs) for better flavor and tenderness. But I have turned older sheep into ground mutton which is fine for casseroles, barbecue sandwiches, shepherds pie, etc. I raise hair sheep so I don't have wool as a harvestable product. But I can sell the hide to local crafters who tan their own. Not much cash in it but it's better than turning it into compost. By the way, sheep are far easier to fence in than a cow, goat, or pig. I really like not having to track down wayward escaped livestock.
Goats - good for milk and meat. Harder to confine than sheep, so you have to invest in better restraint.
Pig - I find that a pig or two is perfect for my homestead farm. They turn a lot of my waste into edible meat. If not well managed, they will ruin your pastures. You just have to keep that in mind.
Between the 50 chickens, 4 ducks, 4 rabbits, 2 pigs, 3 goats, dozen sheep we have plenty of meat and dairy, with lots of excess to sell and trade. It get good variety right off the farm. Plus we trade for fish, beef, mouflon, and cow's milk.
Bees should work fine. I use to keep my own, but when my neighbor across the street got into bees, I gave my hives up. Let him do the work. I'll just trade for a pint of honey now and then.
Fruit and nut trees. Makes sense. Sugar maples? Will they produce in Texas? Maybe look into sweet sorghum instead.
Pond and fish? Sure. Greenhouse? Sure. Hay? You won't produce enough to feed a lot of livestock, especially if two cows are in the formula.......unless your land is lush. A wood lot? Sure but it will take years to establish, just as will your food orchard. Root cellar? Sure unless you're on bedrock. If your house has a basement, then you can create a root cellar there. Water well? You'll have to check with your local authorities and well diggers. They could give you the necessary info.
Energy needs? That depends. A solar or wind system will initially cost a lot of money, depending upon your energy needs. And it costs money and experience/knowledge to maintain. It isn't free energy. I'm totally off grid. I'm happy with it. The system isn't completely self sufficient of course. I have to buy batteries every 6-7 years, distilled water on a regular basis, repair components as needed, and have a generator for topping up the battery bank on no-sun days. The farm doesn't earn enough to go buy a total replacement system. And since one has to go buy all the parts, people will argue, just how self sufficient is that?
From my own experiences, I find that it takes a lot of learning and doing to have a self sufficient homestead. And it takes work to maintain it. But it's a great experience!!! I love having a homestead farm!!!