When I took the DAT a little over a week ago,
For my test version at least, none of the biology questions were anything related to the biology questions on the destroyer... Not even the same topics. The biology is soooooo broad that 1 or 2 specific sources woun't do the trick. I swear to you I had questions on my biology that If I hadn't taken Anatomy and physiology courses I woulda NEVER been able to get the answer right, becuase those questions were asking some general ideas about some systems (I can't mention what cause it gives away the whole question) that were not covered in KBB, AP biolo, or destroyer biology which were the 3 sources I mostly used
With biology, Its random, you might get a version where the test questions are stuff you have covered in AP biology, KBB, and destroyer, or you might get a test version that covers material that is not talked about those 3 sources. And maybe the only way you can answer those questions if you had taken upper level sciences (like in my case)... But I believe the general trend about biology is, 25 are easily answerable, 5 will be WTFs, and the other 10 will require you to spend about 1 minute or more to answer them cause they require you to elevate your thinking.
Now about general chemistry and Orgo, I think destroyer is very good. But I also found the combination of KBB and destroyer and topscore to be a 20+ pusher on these two sections. Seriously I was IMPRESSES with KBB when it came to General chem, I thought it did a great job.
You said you've done the destroyer 3x times, here is what I would do at this point, apply the knowledge you gained from destroyer to another resource (like topscore) and learn from that. Your not gonna get all the questions right, but it will strengthen your foundation everytime you miss a problem.
About QR, I got an 18 so I am not the best person to be giving advice here, but I believe I coulda gotten easily a 20+ on this section If I had done more practiced tests to build up my stamina. I was DRAINEDDD when I got to this section. But seriously, I bought Destroyer MATH, its a book with 10 QR tests and its got a few mini-typos here and there, and I went over the first 6 tests. I am telling you right now, those 6 tests have questions that are VERY similar in nature to the questions I had on my DAT, im gonna go a head and say 80% of them were like SAME questions with different number or different things they asked about.