I PASSED!
In answer to the question on this thread, in the hopes it helps those who come after me - My highest AATBS practice score on a new practice EPPP was 76. I scheduled the EPPP once I scored above 70 twice (72%). I had a 15 day window until my test date, and decided to cancel all patients and do nothing but study until the test (according to the ethics code that I all but memorized, I'm pretty sure "unable to think about anything but the EPPP" counts as impaired enough to need to cancel patients). During that 2 week interval, I re-took the practice tests I had already taken, with my highest score being 84%.
I scored 636 on the actual EPPP, so I don't know what that says about how valid a predictor the AATBS practice tests were. For what it's worth, I felt the actual EPPP was way more straightforward than the practice exams. There were no questions that could have been short stories. Instead of a whole novel about how Gina Gregarious is brought in to your clinic by her boyfriend Mark Morose, with the relevant details buried in a ton of irrelevant narrative, it was a straightforward "Pt comes in with X symptoms and X symptoms for Y duration. What is the dx?" I did feel that the EPPP was very similar to the PEPPO in terms of question structure. I'm not saying that I was totally spared questions that appeared to have been back translated from Greek by Google Translator, because I wasn't. But mostly the questions were fairly straightforward.
For people who hate statistics like me, I do think that memorizing a few statistical facts was very helpful. Memorizing areas under the normal curve, Type I and Type II errors, and having tests associated with their use (chi square is for nominal data, ACOVA allows you to deal with an extraneous variable....) was helpful. Here's where I felt AATBS was not helpful - memorizing facts about statistical tests would not be helpful in answering one of those "short story" questions (A researcher wants to study the effects of five different treatments for ADHD on three symptoms etc. and so forth) but on the actual EPPP, I didn't get any questions like that. They were more "You would use a chi square when the data is?.....) which memorization is super helpful for.
Glad this ordeal is over. Anyone with specific questions can feel free to PM me, I'd be happy to share my experience.