the bulk of the fat normally floats to the top. As it cools, it solidifies. In a fridge, I find that it forms a white waxy layer that floats on top of the stock. I scoop it out with a large spoon (no muslins in the house but that's an idea to catch any small bones as well).
Jelly like - I had this when I put a few carcasses in the pot together. Not sure why. I diluted it down a bit when cooking.
Going like jelly in the fridge indicates that you've made a good, rich stock. It is not fat.
The fat will be a pale layer on the top. It is liquid at room temperature, but solidifies in the fridge. Lift it off carefully with a fork or fish slice, and you will end up with lovely lean chicken soup.