Stop telling yourself you life is hard. It isn't. You're fine. Enjoy it. Embrace it. Hug your Dad, he'll be fading soon. I know you are working your ass off to get into college, it's a valid dream. Don't lose the essence of it, don't forget that your future is in writing more than it is in overpriced education.
You'll get in. Cherish the opportunity. Love your friends more than you ever have before. Appreciate every single person you meet.
Stop falling asleep in class, you'll regret it the day before the final (not because of all you have left to study but because you will finally realize that these classes are actually interesting and you wanted to hear what the teacher had to say).
Get your shit together, don't suspect everyone of going against you. Believe in your value, believe in your worth. You always ned up pushing your friends away because you don't trust yourself to be enough to keep them. Stop that.
Go to the gym more often, you'll miss the exercise. Dance more. Sleep more, I know you feel like you're wasting time but once your father gets sick sleep won't come anymore and you'll need to be rested.
Call your mom more often. She acts like a bitch but she misses your voice, indulge her... tell her your mundane stories about the cafeteria, she'll want to hear them even if they're the same every day. Make her laugh, she'll be more threatened and scared and lonely that you will be, make sure she knows you'll be there even before it happens. Call your brother, he doesn't say much but he'll listen to you talk crap for three hours with a smile on his face.
Love everything you have and everything you are. Life will get hard. Your dad will get sick. You will not have enough money to pay for college even without financial aid. You will not have enough money to fly from Chicago to Colombia often. You will not have enough money for everything. Get ready for it, you'll have to work hard, you'll have to figure shit out the hard way. Maybe you'll pull through, I'll let you know when it happens.