I have to write this...
I'm in the gym, ready to go on my last set of powercleans. One of the bumpers is pretty busted from either overuse or misuse, so it doesn't look or bounce great. Just as I was beginning my set a dude walks up to me and says: "I don't think you're supposed to drop them...
It does put your muscles in oxygen debt as back squats, so your heart rate will increase. Stabilizing the weight isn't easy either, but in back squats there are a lot more muscles working in unison to move the heavier weight which puts stress in your CNS more than the fronts.
In addition to what b fold said, racking is painful if you're new at it. You'll get used to it. I still come home with two big bruises on my delts after workouts, but it doesn't bother me much anymore.
I use 50 dolar VS Athletics weightlifting shoes and they are much better for lifting than any other squishy designer shoe. It really does make a difference.
I wouldn't do a lot of static stretches before lifting. It's shown to decrease your strength and increase the risk of injury. I'd do dynamic stretches/warmups with light weights prior, static stretches after you lift.
There are neck harnesses sold for neck development for fighters. Check out some boxing or MMA equipment sites (title, everlast, ringside). They will work better than shrugs for your goals.
Ephedrine was never banned as far as I know. Ephedra was, and still is, banned. You can get Ephedrine HCL at online supplement stores, though there is a limit to how many you can get.
"The secret behind the P90X system is an advanced training technique called "Muscle Confusion," which accelerates the results process by constantly introducing new moves and routines so your body never plateaus, and you never get bored!"
I don't think I will ever try this.
I think you'll be right back on track once you start lifting heavy regularly again. 2 weeks off could have affected your neural adaptation, but you need those weeks off sometimes.