How much protein from the stock of one large chicken (2kg) carcass once legs, breasts and wings removed? I can find details of how much protein per body of fluid (e.g. 1 US cup) but to be honest we probably all make stock to a different concentration, so that makes that metric useless.

When I prepare a large chicken (2kg), I remove the breasts , wings and legs (and the oysters on the back) so I'm left with just the main carcass which I then simmer for ages.  How much protein is extracted please?
Search on chicken back bone nutrition. Many hits. 

From this link about 20 grams per 102g of total mass.