I am not sure if this will help you in TX, but in CA, this is how I helped save money for a friend.
In CA, we have public health offices, which will give you vaccines for free (only on certain days though). So, whether you are F1, tourist, or illegal, you can have those vaccines for free, as long as your income is below a certain level. So, the friend got all her vaccines from here.
Now, there are also places where you can get TB test for free or very cheap. She got her TB test there.
Finally, called civil surgeons office and informed them that we have all the required vaccines and a recent TB test. Then, the Civil surgeon office did the blood report and signed the paper. Overall, it was about $200.
Something like this probably can be around the DFW area. I would start by calling the public health office of your county and asking them if they provide adult vaccinations for free or sliding scale fee. Even if they don't they will have a list of places which will do this.
Moreover, i693 do not need to be sent with the original application. You can take it with you on the day of interview (that is what she did), so you will have enough time to search and find a reasonable civil surgeon.
Best of luck!
