What gives you the best chance of making that salary is getting hired by a big firm. Here's what gives you the best (but not the only) chance at biglaw:
1) Transfer somewhere other than SMU, someplace higher ranked, like UT. (I assume you want to stay in TX?) SMU is a good school with a good regional reputation, but biglaw jobs are incredibly competitive. You'll be competing against others who are also top 2%, law review, etc and from bigger name schools. Those firms are snobby, and pedigree matters.
I'm sure that some SMU grads get hired into biglaw, as I said SMU has a good regional name. But if you want to know what gives you the best chance at biglaw, try to transfer to someplace like Harvard, Yale, Penn, etc. In this market I'm sure that big firms in DFW get applicants from those schools, and you'll have to compete against them.
If you want to live outside of TX, try to get into a nationally recognized school.
2) Remain in the top 5-10% (at least) after you transfer. This is not as easy as it sounds, as you'll be competing against a different, higher performing class. Try to get on law review, if possible (sometimes not open to transfers).
3) Obtain a biglaw summer associate position, and do a great job. Most of the people I know who went into biglaw worked summers at a firm and made connections. The only potential snag I see here is that your first year and half worth of grades are from a lower ranked school. I'm not sure how biglaw would view that.
With that said, here are a few other things to consider. Biglaw is not the only satisfying or even lucrative area of practice. Plenty of lawyers who are solo practitioners or small/mid-sized firms partners do just fine, comparable to biglaw partners. I've met a guy who has a small firm that specializes in class action suits, and could buy and sell most biglaw partners with the change in his pocket. Being a DA or federal attorney isn't too bad, either.
Biglaw is one of the few areas, however, where you can make that kind of money straight out of law school, so I understand the attraction. The hours required and the stress level are high, and many burn out quickly. That's one of the reasons you should do a summer biglaw job, to get a flavor of the practice.
It's also possible that yo could get hired into biglaw coming from a smaller name law school, like the one you're at. I went to a local school, and some of my classmates were hired by biglaw. You have the grades to be competitive, but I admit I don't know the TX market at all. If you could negotiate a better scholarship at your current school, however, it might be worth it.
You have to accept that even with awesome grades you may not get hired into biglaw. These jobs are limited in number, and you won't be the only applicant with a high GPA. Make alternative plans, scope out smaller well-paying firms, and gain as much marketable experience as possible.
Hope that helps, and good luck!