Don't worry about getting "fat" and not being lean. Yeah you might not have that 6-8 BF% you want but you'll be hard pressed to get over 10-12% and that's while eating like a maniac. Good old heavy lifting burns a lot of calories and when you do decided to "lean-up" for summer all it takes is not putting an extra 1/4 cup of olive oil on your salad and rest will take care of it's self.
Warming up with OHS seems like a good idea but I think you should warm up with regular squats instead. Getting your form down right and getting a feel for the bar is essentially to squatting heavy, especially sets of 5. Warming up with OHS and then jumping into a heavy back squat set doesn't sound like fun.
Getting coaching for the O-lifts is a great idea even if you have no plan to compete. They're a great tool to add to your arsenal.
I've been following SS for a bit now and I've really enjoying it. There's something so satisfying about plain old lifting heavy. That and the fact that I'm angst ridden and stressed out over life lately and the iron is a great therapy device.
What's your current weight and height and lifts look like?
Fasting is still good and I do them every couple days or so. Just means more eating in a smaller time frame. I like food so it's all good.
My last comment would be for you to go out and buy Practical Programming by Rip. Seriously a great book. I think if you read that you'd rethink going to the PM mass-gain template and just tinker with what he's laid out in there. No disrespect to the PM template...
Healthy body sick mind...