Riyaz,
Congrats on the improvement in the 2nd exam. Of course, the PMP exam prep is different for everyone and no "plan" can guarantee success on the actual exam. Some can get by with only the free exams while others may only need to take a boot camp and can then pass the exam. I personally do not think I would have passed if I had not used the PMP Exam Simulator. It really was a critical component of my exam preparation and definitely helped me prepare for and pass the actual exam.
Below are some answers to the questions you posed:
1) There could be a few non-PMBOK questions on the exam but I would not get to wrapped up in studying for those too much. Your main focus should be on the PMBOK guide.
2) Whether you go through PMBOK and Rita's book again is entirely up to you. If it were me and I had the time I would do it. It can't hurt. I actually read through PMBOK completely 3 times and then reviewed certain parts a 4th time. I didn't use Rita's book at all but in retrospect I wish I had. You should definitely determine your gaps and focus on those.
3) I would not panic if you take an exam and score less than 75%, but it you do that more than once on consecutive exams you should try to determine what may be the cause of the lower score. Try to simulate the exam conditions as close as possible.(e.g. Set a 15 min. timer and do your brain dump before your starting your simulated exams. You should really strive to do this in less than 15 minutes.). Also, you should be doing your brain dump at least once per day at this point.
4) That sounds like a good plan. In the last few weeks leading up to my actual exam I was finding it difficult to block out an entire 4 hour period. I had already taken 5 or 6 full exams to that point. So, I just used the PMP Exam Simulator timed mode and took multiple 25, 50 or 100 question timed exams since it was easier to block out an hour or two. I still had the time pressure which is very important. At that point for me I felt it was more important to answer as many simulator questions as possible and I think that strategy worked well. I think it is very important to take as many full exams as you can because it really is a marathon and you have to prepare yourself for it. However, don't burn yourself out. Bridging the gaps during the weeks is a good plan and you might also fit in some shorter timed exams (even 25 questions) just so you get practice answering more simulator questions. Note that you have the option to select "answer only unanswered questions" when setting up the shorter timed exams and you definitely want to do that.
Good luck in your preparation efforts. Keep at it and stay focused!
Cheers,
Mark