Chemistry SAT 2 Practice Tests and Advice?

Hello everyone,
I have now taken 3 practice tests for the Chemistry SAT 2 (June 6) and I am beginning to get worried about a few things. First off, on the first two practice tests I took I scored a 600(Barron’s) and a 580(PR) which is not that great. However, I just took my third this morning and got a 670(PR). The only thing I had really done between taking these was look over my missed answers and do a bit of flash cards so I have started thinking that perhaps the PR second test is messed up in that it is a bit easier than the others. This could, and most likely is just me being really nervous though… If anyone else has taken these and has any ideas please respond. Secondly, the test is about 6 weeks away and I only have 3 practice tests left… I just ordered the Kaplan book online as well as the CB practice test but still that only gives me 7 and I have taken 3 in the past 2 weeks. Additionally, I heard that the Kaplan books are not even very good for preparation. Anxiety is killing me right now and I could really use some guidance.