Please get the *8th* Edition as the study and exam content changed in 2018 and the book was updated accordingly. BTW, for those who are not aware, the Sybex book is the Official Study Guide.
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):