spending time to get into top school PhD vs getting done with PhD
I think you are vastly overestimating the value of ratings from a popular magazine as they apply to doctoral education and vastly underestimating the quality of doctoral education at any R1 in Texas. 

Frankly the real difference, in an individual field between a school rated 180 and one rated, say, 40 is likely to be a mix of random and the value of a given helpful advisor. 

Frankly, I think you would be wasting your time to do much of anything but take what looks like a very nice offer. You'd be halfway through a doctorate at the Texas place before you had a chance to start if you go another route. If you read a lot of questions on this site you'd notice how lucky you would be to have found a good and supportive advisor. Many are not so lucky. Who can say whether you'd have a better time of it if you look elsewhere? 

And it is you that makes your career, not the journalist/researchers at US News rating places on general criteria.