I obviously don’t know anything about your situation beyond what you’ve just posted, but I can say that if your parents are like most parents…they want you to do what’s best to make a better life for yourself. This is a rough situation, but I’m sure they don’t want you to sacrifice your goals to take care of them.
3.5 hours is a long drive (keep in mind that that’s 3.5 hours -both- ways), but it’s certainly doable with some careful planning. As previously mentioned, you’d want to plan it around your schedule at school. If you have three exams coming up next week, then this weekend probably wouldn’t be a good one to go home. However, if you have three exams this week, you probably won’t have any next week, so this coming weekend would be a great weekend to go home.
You could even potentially use some of that driving time to your advantage. If you learn well by listening, recorded lectures and such could be a great learning tool so you can continue studying while driving. This wouldn’t work for me (a physics major), or for a chemistry or math major, but for someone majoring in history, sociology, foreign language, etc., it would be great.