That seems like a pretty normal first time through. Don't get disheartened! The first time I went through the DAT Destroyer, I got destroyed! I was very concerned about how I was going to do on the actual DAT, and a little disheartened that I wasn't getting 80%-90% correct. But as others have said about, it is just a tool for studying and it is not relatable to the actual difficulty level of the DAT.
Keep studying!
Best of luck