i havent taken the DAT yet but the first time I ran through the Destroyer I got 50% or more wrong, it was awful. But I tried my best to learn why I got things wrong and now when I'm doing it a second time I'm only missing 20-30% and sometimes less. I think it's important to understand the concepts of why you missed something, for example I kept missing those stupid equilibrium problems with the RICE tables. I tried and learned how to do them properly and now I don't miss them anymore. I don't think you need to "memorize" the answer though. The Destroyer just helps point out some flaws in your knowledge to make sure you're really ready for the DAT.
memorize, learn, same thing. whatever it is you do so that if a similar question comes up on your test you'll know the steps to take for the right answer. imo, the only subjects that you should blatantly memorize are bio, a handful of ochem reactions, and trig functions. and when i say bio i mean campbell's or cliff's not destroyer.
I wrote note cards for the chem and bio questions I missed and reviewed them as much as I could. I got tired of doing it for bio because there are a ton in destroyer, so I started typing up everything in the answer section and reading over that.
My plan was to be able to at least recognize what they asked. There's so much material, bio especially, you're better off making a few educated guesses on some problems than focus on specific stuff and have no clue on other questions. That's how I did it, you may find success doing something else. Find what works for you and go with that.
Best advice anyone could give you is to stay relaxed, if you worry you waste precious time. good luck!