Fire ants are very different from regular ants. A lot of people are giving advice that is not applicable.
Regular ants are attracted to sugar/sweet things, hence the borax traps mixed with corn syrup or sugar water. Fire ants ARE NOT attracted to sweets, they are attracted to fats. They will not consume and bring back to the hive any bait that is sweet. Borax will NOT work on fire ants. I live in the land of fire ants and have been battling them for almost a decade. I've tried every DIY suggestion I could find to avoid pumping poisons into my ground and none of the home remedies work.
If you want something safe to use near/in an area where you are growing edibles the only option that will actually work is spinosad. The best formulation I've been able to find is Come and Get It. (It's much more effective than drenches, which I've also tried). Before you sprinkle it around mounds, make sure you test to see whether the ants in that mound are actively foraging - I use corn chips placed near the mound and check on them in 1/2 hour. If the ants have found the chips and are bringing them back to the mound, it's the right time to sprinkle the Spinosad.
First of all, gardening can be really fucking hard. It would probably take me an hour to list all of the infestations I've had to deal with in the past year. Some people have an amazing garden right out the gate but most of us need time to figure out what really thrives in our climate/soil/grow set up. As for feeling discouraged - I've been there. It sucks when you feel like you invested a lot and have nothing to show for it. The only thing I can say is that it's a learning process and it will get better.
First, have you checked your state's extension growing calendar? (If you don't know what that is or where to find, let me know and I'll see if I can help). I'm not familiar with your area's growing season; don't assume it's the same as people in the north. It might be that you're trying to plant some things at the wrong time of year. I'd be really surprised if this is the right time to start broccoli sprouts in TX, but I could be wrong.
Second, some plants do really well in fabric grow bags and some do not; grow bags dry out REALLY fast; so the issue with the tomatoes might be that they're drying out too quickly, especially in high heat. You might need to do some experimentation to understand which plants will thrive in grow bags, and which prefer to be in the ground (or a plastic pot). Can you plant a few (or even just one) in the ground to see if it does better there?
Third, peppers can be a bit tricky. I've found that while everyone in the north has theirs in full sun, down here they don't tolerate full sun at all - mine get morning sun only. And even with that, they still struggle when it's over 90F unless I keep them really well watered (sometimes even 2x/day). See if giving them more water or less sun helps.
Fourth, fire ants. Order some Come and Get It Spinosad granules and show no mercy. I live in the land of fire ants and have tried everything under the sun. This is the only product that I've found to work (and isn't toxic to everything else). If you have any questions about how to use it or test whether ants in a particular mound are actively searching for food, let me know.
Consider this your trial by fire phase. By dealing with all these problems right from the beginning, you'll know exactly what to do (or not do) next time.