I agree with SuperG, it's 2-3% of his adult weight not current weight as a puppy. When Eugene was that age he was eating ~2.5lbs a day. He would never have survived on 1.2lbs! He's currently 11 months and a long lean 85lbs eating ~1.75lbs/day.
Yes you need to feed variety but not necessarily in the same day or week even. We feed premade raw in the morning because that is what works best for us. It's generally either beef or venison but sometimes quail, duck, or turkey. Dinner is often a chicken quarter or pork. Sometimes he gets a whole rabbit and that's it for the day. For organs it's generally liver and kidney (I'm working on expanding this). I portion it out in weekly amounts in ziplock bags and freeze pulling one out each week and ration it out through the week.
I personally don't feed necks or backs but I know a lot of people do. I add fish oil to every meal and vitamin E a few times a week.
Check out Lauri's website Welcome to the Raw Dog Ranch
, I found it extremely helpful when I was starting.