Sorry to hear you did not pass nbde part 1 same here and I took Inbde do not worry its MUCH easier.
It’s not recommended that you buy DD most people on facebook say it’s the same as the old ones.
I took my inbde last week. My study materials were dental mental slides + mastery app + crackinbde.
I found DD 2013-2014 pdf online and I studied ( pros, pedo, radiology, practice management ). I do regret studying it because the content was NOT high yeild.
if I go back in time I’d do dentin or the study boards.
there is a dentin file summary of most important facts around 200 pages only as opposed to the original~1000.
if you want to do DD do not go though all of it find a summary for it. Someone did a very good summary of operative facts from DD and you can find it at inbde telegram group.
I recommend you focus on clinical dentistry + pathology + pharma + practice management