i am your same age and 1.5 inches shorter.
i don't know what ideal protein is. for your transition, there is no need to fast (unless you want to) and juicing is not a good idea for anything.
do you want to stay low-carb? what are you eating now? when you say "naturally sweetened" are you eating any fruit now? a few servings of fruit should not spell doom for you. it's a nice treat with yogurt or real cream.
fat is indeed considered on primal, it's not a free-for-all. you need to use some common sense with regards to what you consume.
As I ate the oysters with their strong taste of the sea and their faint metallic taste that the cold white wine washed away, leaving only the sea taste and the succulent texture, and as I drank their cold liquid from each shell and washed it down with the crisp taste of the wine, I lost the empty feeling and began to be happy and to make plans.
– Ernest Hemingway