I will also offer my opinion-
First, good luck! It will be a lot of work but you will get through it and it will be worth it.
1. I would study around 1-2 hours on nights that you are busy and put in 3-4 on weekends or nights you aren't busy with your school work. Do not let your grades suffer because of this test!
2. I mixed subjects, around 2-3 a day depending on how many hours. I stuck to about 1 subject an hour.
3. I highly recommend DAT Destroyer, Math Destroyer, DAT Bootcamp, and Cliffs AP Bio Edition 3. Don't waste your time with the Kaplan course, you can do more on your own time. I did not like Crack the DAT because I found it to be too easy. DAT Bootcamp is the much better alternative.