A lot of what you talk about seems to be on surface level anxiety related. I had a big freak-out when I took my April exam as I didn't feel that I was ready, and ended up scoring below what I was making on PTs. That being said, it feels great to have gotten it out of the way. I now know what to expect, and that's been tremendously helpful with the psychological components of the exam.

Personally, I think you should take it and cancel if you're unhappy with the score, as that way at least you have something on file and you've done it one time. Then you get another two months to study. I know many people state that they dont start to get results until several months in, but that it takes time before a breakthrough occurs. You can do this!