Guess you originally came from China. Based on my guess...
If you are OK in your chinese high school g-chem, you are over-prepared for your g-chem in DAT, and if you are OK for your middle school g-chem you are well prepared. For o-chem, u need spend time in preparing, but it is way easier than your university level o-chem. Biology is tricky if you want to score high, coz i know chinese education sys pay little attention to biology. Spend enough time in your Kalplan Book Biology section. A middle school chinese student can score 20 in the DAT math part, as long as he can read the questions. PAT is wierd, defintely use Barron.
Now the left part is RCT(root canal treatment or reading comprehension test😀 ). It differs from people to people. If you came here since you were in primary school, guess you will be fine. But if you have been here only for couple years, watch out! RCT is the most DIFFFFFICULT part for non-native speaker. I scored 25,25,24,23 in my sciences, but screwed as low as 15 in my RCT. You need to get prepared. Get the habit for reading daily. Focus on this part.
Those suggestion also work for non-native speakers from lots of other Asian countries and regions(Korean, Japan, India, Hongkong, Taiwan etc.), since the Math-Chem-Phys fundamental education is so hard over there.
TA is not so helpful in your application. If you really need money, do it. If not, you might choose to shadow the dentists, work in the labs or do some volunteer work.
If you came from China, hope this will be helpful. If you are not, read this as a joke.
Anyway, Good Luck.