1. You decide how you want to use your break time. You get 45 minutes, plus whatever is leftover from the 15 minutes you get from the tutorial (for a maximum of 1 hour break time). So if you have gone through the tutorial with the free 150 questions, you shouldn't need to do the tutorial at the test center (just check your sound).
People do the split many different ways. I had planned to try to do 2 blocks and then take a break, but I ended up needing to break after each one. I took a longer break (~20 min) after block 5 for my "lunch" (it was actually around 5 pm, so not really lunch). Make sure to take a short break before the last section and don't rush through it. Also, keep in mind that you have to sign in and out for each break, so this will cut into your break time.
2. Bring high-energy foods that you can eat quickly as a snack between blocks, and then bring something a little more substantial for your lunch (but not too much food). I brought 2 granola bars (but only ate one) and a banana, plus nuts and dried fruit. I had a half a bagel and some pasta salad for my "lunch". Small sandwiches are good too.
3. The prometric centers require you to be there at least 30 minutes before your exam time. Usually, the earlier you get there, the earlier you can start, as long as they have a seat for you. I had a 12:30 scheduled start time but I got to go in at 11:40, which was really nice because then I got out almost an hour early too.