Good questions -- and good luck... wanted to share a few thoughts on your questions:
1. Developing that focus is tough -- it just requires practice. You're literally building muscle memory for your body to sit and focus on a task for more than 3 hours (admittedly, something that not many of us do on a regular basis in this adult-ADD world we all live in.) That said, try not to think of it as 3.5 hours. Think of it as two somewhat-important 30 minute sections, with a quick break, and then two pretty important-75 minute sections. What stinks of course is that the less important sections come first (when our brains and bodies have the most energy.) You'd hate to get 95% of the way up Everest only to run out of energy. Same thing here -- need to figure out a way to prioritize and stretch out that energy.
2. Remember, your goal is to win the war, and not any specific battle. You need to think about both time per problem, and where that fits in the context of the full exam. Don't go crazy worrying about the first ten questions more than you would any other set of 10 questions. Remember -- you will get questions wrong. It's the nature of the adaptive test.
Hope this helps.
Brian Lange | Manhattan GMAT Instructor | North Carolina
Manhattan GMAT Discount | Manhattan GMAT Course Reviews | View Instructor Profile