That sounds incredibly stressful and difficult, I'm so sorry. Nobody should have to endure 16 hour days (especially with a job like that, where you're driving, so if you get tired you're risking your own safety and others). Plus, everyone needs time to unwind, relax, and be off the clock.

I don't have any good advice. I hope going back to school works out for you, and that if you decide to stick with the delivery job for a bit, until you find something else, that the hours get back to normal soon. (Do you expect things to be back to normal after this weekend, or will there still be a lot of late deliveries to make over the next few days?)

Oh... and let me also say, thank you for what you do. I just got a surprise package from my mom. I live far from my family and am pretty socially isolated, so the surprise really brightened up my holidays, and I'm very grateful that there are people out there who are willing and able to make package delivery happen (though, as I said, I very strongly think you should be treated better, and not spend every waking moment of your life working!)

*thanks* and good luck with school and the future!