Make your body clock work for you. Don't fight it. If 2 PM works for you, then go for it.
You can improve both in verbal and in quant. I found the Advanced
MGMAT Quant book very useful, but I can say that GMATCLUB's maths questions are also very helpful. You should cover all the Maths books from
MGMAT as they are really good. This time try to focus both on questions and answers. GMAT maths is very easy, but you need to practice a lot. There are set patterns and this is where doing a lot of questions help.
Let me know which books you referred to for verbal as I can suggest you a few. I had real problems with verbal in the beginning as I never paid any attention to grammar - never needed it for becoming an engineer, but now I can easily spot errors in most of the English Newspapers and Websites in U.S.
Don't get side-tracked by the age issue. One more thing, I took Red Bull this time and rather than helping me, it made my head spin a little. So if you plan to use it, try it on your practice tests. Due to working in software field for long time, my eyes get dry a lot so I took some eye drops ( Refresh Plus) to the test and used then in each break. By the time the verbals come, my eyes are always red due to dryness, so I try to finish the quant ahead of time and don't submit the last question. I use this time to close my eyes for 10-15 minutes. All in all, try to find out what bothers you during the test. This you can do by taking full length tests. Timing is very important and GMAT WILL TRY to upset you. Don't bother. I think I failed to achieve my target score due to paucity of time in the last 12 verbal questions. I got a passage of more than 600 or 700 words, and that upset my rhythm and the fact that I got 12A(13) number terminal, which did upset me in the beginning. I will try again to beat this "monster" GMAT.

Have full run of tests and take all the sections, including the AWA. This will take care of a lot of your test day anxiety. One more thing: tell yourself 100 times that GMAT can be taken again without too much of delay. It will help ward off the test day anxiety.