1. This isn't 100%, but a totally blank section leads to a score of 200 for writing and about 250 for reading.. He would need to get over 400 on the Math to have a shot.
2. A 2 is the lowest possible score, and a thesis will get him that. Teach him how to write a thesis, two 1-2 sentence body's using simplistic language, and a conclusion, and I think that will get him a 4-5 on the essay.
3. 27 right 27 omitted is indeed a 500 on most exams. You have to understand, however, that he will have test day pressure and make mistakes. Getting 35 correct and about 8 wrong will still net him about a 490, so he should be set.
4. Not sure.
By the way, -0 and lower on writing is all 200. Even if he got every question wrong, he would still get a 0, and if he omitted every one, it would stay 200. I would tell him to christmastree the entire section and take whatever points he can get.