Couldn't snap the bones in my chicken stock
With all respect to Alton Brown, "snapping" the bones is not a test I have ever heard of.  He does not mention that in the official recipe on the Food Network site.

I just watched the entire episode on youtube, and he does show the snapping thing with a very frangible bone.   I think this result will depend on the age of your chicken and the size of the bone.

In general, the thinner bones and younger chickens may be somewhat rubbery when a chicken stock is done.

8-9 hours also seems excessive for poultry stock, although that is actually in his recipe.  You should get the vast majority of the flavor (and nutrition) in 3-4 hours (plus maybe a little bit to thaw, if you are starting from frozen), especially if you have chopped your carcass up into pieces or chunks (which he did not discuss in the episode).