Are there any books/guides/things I can study or do to be able to excel in the Harvard II? I'm trying to prepare as best as possible.
Besides being familiar with the BGA-100 and RCAF FOM, pre-studying isn't going to help. The learning curve on Phase II is steep but doable, you will have more than enough time to learn everything you need to know once course starts. Chair fly and learn your red and white pages cold. I used to sit in front of a poster of the cockpit and do an entire startup, shutdown and all the red pages each night, and it paid off. The better you know you shit before you get in the cockpit, the more brain cells you can dedicate to flying the airplane, where the learning curve is steep and not nearly as flexible.
I tend to be nervous on exams/flight tests
Do you just get nervous or does it affect your performance? Being a military pilot means you will live a life of constant tests and evaluation. It's ok to be nervous, but if you can't perform under pressure you may run into problems. When I went through Moose Jaw, there was a guy on my course who would be so nervous he would puke before every test, but he did just fine. Another guy was equally nervous but let it get to him, he was gone in no time.
The fastest Aircraft I've ever PICed in is a DA40, so nothing anywhere near the harvard II.
Then you've already flown a faster plane than every other student on your course, they are all coming from the Grob. Don't worry, you will get used to the speed.
I need your help to guide me and give me any sort of advantage to compete and be the top of my class so that I can be selected to fly CF-18s.
Go in with an open mind (especially important for guys with previous flying time) and work your ass off. There is no secret to getting selected jets; hard work, skill and don't suck.
Oh, and go to the mess on Friday nights, seriously. The Moose Jaw mess is one of the best out there, and blowing off some steam and celebrating your victories/drinking away your failures as a group helps a lot. Looking back years later, Friday nights at the mess are the most memorable thing about my time there (even if I don't remember all of it...). Just don't steal the KFC delivery car, those guys got in a lot of shit.