I can't help completely as although I have raised both an 8 week pup and a litter on raw I do not actually use the BARF system. The way a did it was to split the feeding into several meals so 8 weeks to 4 mths got 4 meals per day. one was just milk, one was a cereal meal and 2 were meat with bones. The meat content started off at about 50mg per meal so roughly 100mgs meat per day plus the small cereal meal and the milk.
4mths to 8mths I stopped the milk in the morning but continued with the milky cereal which I increased and slighty increased the meat meals for the 2 evening meals, possibly to around 75mg per meat meal.
Once they reached 8 mths they went on 2 meals per day, the milky cereal in the morning and 1 meat meal in the evening followed with bones. This was probably about 100mg per meal although could have been a little higher.
I didn't really weigh anything, just had an eye for what was right. I judged it on the pups activity level and by feeling the pups ribs and how quickly the food went out of the dish (not very scientific or helpful to you I know).
The use of cereals is were the diet I follow differs from BARF as in general BARFers either prefer no or very limited amounts of cereal in the diet.
I guess reading the BARF book feeding guide for the puppy you would be looking at feeding between 5 and up to possibly 8 % of your pups weight.
I did have a weight guide that I gave to my pup owners as a guide to their cockers weight just for peace of mind, which was roughly correct for my litter, but as I've said it's only a guide, not gospel as looking at your pup is much more realisitic as to whether or not you need to increase or decrease food amounts.