I read many posts from people who failed the new CISSP adaptive exam. I myself failed it on 3/5/18. I expected to do 250 questions but I was very shocked that I got knocked out after 99/100 questions. I asked the proctor whether I was given the wrong exam. The proctor explained to me that because it is an adaptive exam the so it stopped because I didn't answer a certain number of questions correctly; I was absolutely horrified what I experienced. I could not sleep all night after the exam day, I've been studying for it for over 3 months and I scored between 77% - 85% of dozens of practice tests of over 3,000 questions. I went beyond by reading front to back cover of the Sybex - 7th Edition book and I completed all the chapter tests as well as all of the online practice tests that Sybex offered me and I did well. In addition I also went through all of Cybrary training videos, figuring that with all that studying I was well prepared to take the exam. Not to mention that I have a master degree in IT and in Information Assurance field with the company for over 9 years.
I find the adaptive exam questions and answers are so abstract that I feel my English comprehension isn't good enough for it. I have reached out to ISC2 for their support and advice. I am so sad and disappointed that I am not sure if I ever want to take any test in the adaptive format.
Yes, purchase the latest ones, because his students update him on how the exam went and he focuses his content accordingly. ISC2 seems to have dropped a lot of the math and some of the more granularly technical questions and focuses more on the policy management. So I wouldn't be surprised if his newest videos focus most on "What's the FIRST thing you should do when..." types of scenarios.
Since you've already studied the material, you should do Boson, and at the same time study those subjects that you don't understand subject by subject using the latest Sybex and AiO. And watch the latest Greenblatt videos ($100 from his website). You should ask for the latest, since he does classes every month or so.
OJT helped me more than any other resource when I took the exam, yet strangely it rarely makes the study lists. For me, it was the single biggest factor for making the exam "easy".
My personal recommendation (in order):
Hint. Its not necessarily the ISC(2) writing these exam questions but members of the ISC(2). Every couple of years we have the opportunity to come together for a few days and write exam questions in a workshop type environment which has been "reported" to be a great deal of fun. Not naming names but you get the idea.
Everyone has a different take on questions and where to start. I wouldn't necessarily look to NIST but being well regarded, could certainly see no argument to doing so.
You know not performing as you expect is just a step along the way to performing better in future. So you failed a test. I failed my driving test a number of times, but didn't blame the examiner, the other road users, the road layouts, the route of the test or any of those things. I just went back to my instructor and practiced the things I got wrong. It's really just a matter of doing the right preparation and on the balance of probabilities you'll pass the next time.