Hello Workx!...I would say that if you can get through the NCEES practice exams on the FIRST pass with a score of 55 or better you have a very good chance of passing the real deal. Did you time yourself when you worked the practice problems (full 8 hours)? This is very important as it'll help train your brain to work under the time pressure, especially after 6 hours of hard concentration because you start making silly mistakes.
With respect to the types of problems on the practice exam and how they correlate to the real exams, make sure you understand the concepts and do as many similar problems as you can. You are correct NOT to expect to see the same type of problem set up, that's why it's so important to practice, practice, practice so you can fine tune your problem-recognition skills. Half the challenge with these problems is understanding what they're asking you to do, so make sure you read the problem statement twice so you don't end up doing unecessary work and waste valuable exam time.
To answer your last question, I was not able to finish within the alloted time ANY of the 4 times that I took the exam, BUT, I didn't let that bother me. Remember, this is about getting 55 questions right, so make sure you go for the low-hanging fruit first. Reading through your last paragraph I can see that you're already thinking along these lines which is great. Go for the easy ones first and then on your 2nd, 3rd or 4th pass go for the most difficult ones. Make sure you allow yourself enough time to bubble in the ones you have to take a guess on and remember, if you're absolutely lost and have no idea what they're asking, the answer is "B"....at least according to Dr. Tom. As a reference, the last time I took the exam I had to guess on 2 questions in the AM session and 2-3 in the PM.
Good luck with the rest of your studying... just over a month to go!