Dont skip, but rather start reading from the end, or first find out that "question" in the sentence then go back to scenario so you may ignore other scenario given that are not related to the question. Many questions could be written as - many scenarios first (paragraph) then at the end or at least 2 sentence before the end is the real question.

Most of the people complete PMP exam in 3:30 hours. So managing time of 4 hours should not be of any concern. Take break for 5 minutes 1-2 time.

I do not support marking questions and keep a queue ready for the last moment. Although, every human has different style but I feel when you put an effort to read a questions, solve it the same time because when you mark it and open it again at last, you actually put double efforts and double efforts might lead to dual thinking i.e. confusion.

For lengthy situational questions, use the same technique the way you watch a 3 hours movie. Do you remember each and every dialog of 3 hours movie you watch? Ofcourse no, but you still understand the story, right? Take long PMP questions the same way, look for keywords, try reading fast and try changing the reading sequences (as projmanpro has said). In short, these cannot be taught and documented, it comes from within and when you practice lots of mock tests, such techniques automatically comes in you. Hence I always emphasis on taking more and more practice tests.

Good Luck!

Saket, PMP