Wow! You really need to go to a therapist and get your priorities straightened out (and I say that in a loving way). Briefly, you are doing nobody any good sitting in a frozen death vigil. You are best able to help by moving forward with your life.
Sure, 3-1/2 hours is doable. You may wish to schedule out 1 weekend a month (coordinate around mid-terms, finals, sports, other activities), to come and add a boost of assistance to your brother. You may wish to identify specific key activities and schedule them for each trip home that will be a real help (get car services, clean and organize kitchen and re-stock pantry, seasonal major tasks, etc.). Your brother has the basics covered- maybe doing some of the extra’s would be a good thing. With a very defined schedule and very specific plans & dates for contributions, I think everyone would be happy. It would be an enormous burden on you, but at least you will be living into your future, rather than being frozen, paralyzed in this present reality. And you will be better positioned, 2 - 3 years down the line, with a degree (and maybe a job), to be of REAL help.
You need real-person dialog to see the larger context, put a plan in place, and have the courage to act. Congratulations on seeing what you need to do! Good luck!