I had a reasonably good understanding of A&P, Pathophys, and the like. I generally did well in Nursing School, my prerequisites, and so on. I had a SOLID 85% average... For Nursing School, that's GREAT!!! I passed the NCLEX in 75 questions. I've never taken an adaptive test before. All my exams, even though many of them were on the computer, were essentially like a pre-printed exam. That includes my NREMT-P exam that I took 15 years ago. That had 150 questions and we had to answer them all.
Here's how I approached the NCLEX exam. The NREMT exams are also adaptive, incidentally, so a similar approach may work for you, if you know the material and you have a hard time taking exams. I noticed that you went over and over and over the questions...
First off, understand that the questions will NOT require you to invent a scenario. It will require you to answer the question based on what you know, given the information provided for you in the question. There will be no "but what about this situation..." type questions present.
Second, when you get a question, you should read the question, then read the answers. Do NOT answer the question just yet because you may have misread the question (I've made that mistake too many times). Then go back and re-read the question while keeping those answers in mind. Now read the answers again and kick out the two most unlikely answers from consideration. You now should have 2 questions. One will be the most correct and the other one will me mostly correct. Look for the phrase/word/info in the answers that will make the question actually wrong. The one left standing, you should re-read it and make sure that it makes sense and answers the question without "what if" in there. Choose that question, submit your answer for scoring and move on to the next question and start this process all over again. How long should this process take per question? Less than a minute.
Third, answer the question ONCE and move on. Do not change your answer as statistically it's going to be more often correct than not.
Fourth, if you get "select all that apply" type questions, you should rejoice... each answer is simply a True/False. Each question must be all "true" to be selected. Otherwise, you must consider it "false" and not select that part of the answer. Evaluate each "answer" statement independently as its own true/false statement. Once you have evaluated each statement and decided if each satisfies the question, submit and move on.
This all perhaps sounds complicated, but it's really not. The adaptive exams will find your ability as long as you know the material. Trust me, the NCLEX was the most difficult exam I've ever taken and I KNOW that after about question #15, I probably FAILED about 50% of the answers... but my scores were high enough to allow me to pass within 75 questions (minimum). If you feel that you did well, then chances are good that you failed because you were probably answering very basic (below passing standard) questions. If you read several different forums where students have to take adaptive exams for licensing, you'll notice that almost everyone that passed felt like they failed or did very poorly and wanted to puke... It's because the exam is adaptive to YOU and will find your ability for that day, at that time.