I want Army to be my full-time career as I am expected from y family to become as high ranked as possible.
I'll give you some unsolicited advice about this one. If you are ever given the privilege and honor of commanding or, if not in command, then supervising our military's most valuable asset - its people (civilians and those in the uniform)- you MUST always put them first while accomplishing your mission. If you do that, then rank will come. If you're in this to make rank, then rethink your motivation to be in the military because you'll be sorely disappointed when you don't get promoted. I see too many people go into this profession for the wrong reasons and they get found out relatively quickly. Their evaluations will reflect the results of any misplaced priorities they may have.
OK, so you want to go to medical school, specifically USUHS. I tell people 2 things about getting to medical school. The advice is applicable to getting into USUHS as any other medical school.
1) It's all about GPA and MCAT. That's it. Of course, there are other aspects of an application such as ECs, leadership positions, etc, that are important, but at the end of the day, it's all about the GPA and MCAT scores. You'll apply to many medical schools (it's in your best interest to cast a wide net), but you'll get secondary applications based on what you submit about yourself. Many medical schools screen for those with high GPA and MCAT scores and will send secondary apps only to them. Don't get me wrong, you've still got to do some ECs. Do 1-2 ECs and be passionate about them. Dig into those ECs. Don't just join ECs to pad your resume. Adcoms want to know you can be passionate about
something. The reason is medicine is a grueling training path and lifestyle. You won't be happy in medicine if you're not passionate about it.
2) Major in whatever you want. You don't have to be a biology or chemistry major. If you love to dance, then be a dance major. If you love math, then by all means be a math major. Enjoy your undergrad years. You'll also probably get a high...guess what???.. GPA in your major because you love it. That said, whatever major you select, you must choose a
pre-med curriculum. In general, a pre-med curriculum entails taking courses that are required for almost all medical schools - 1 year of biology with lab, 1 year of general chemistry with lab, 1 year of organic chemistry with lab, 1 year of physics with lab, 1 year of math (calc 1 and calc 2 or stats), and 1 year of English comp/writing. That's really about it. To do well on the MCATs, you may want to add in a class on sociology, gen psych, cell biology, or biochem (some med schools will allow you to sub biochem for a semester of organic chem). Does this mean the high GPA in your major will carry the day? Yes and no. Medical schools look at your overall GPA and your biology, chemistry, physics, and math (BCPM) GPA (the latter is also known as your science GPA). They want to know you can handle the obviously science-heavy curriculum of the first 2 years of medical school. During your undergrad years, you will want to keep an eye on both your science and overall GPA.
I think you'd have an advantage of getting into USUHS if you're part of the TAMU Corps of Cadets. It will show the USUHS adcom that you have some motivation for the military.
Your back-up plans should including applying for civilian medical schools and the Health Professions Scholarship Program (HPSP). Fortunately, you're from the great Republic of Texas ("God's country" as many Texans I know call it), so you have plenty of good medical schools (public and private) in the state.