wrote:
> [snip]
> First off, if I can't use chicken fat, what is a good substitute?

Oil, as the package says.
>
> If I skim off the fat after cooking the chicken, will some of it seep
> back into the broth? [snip]

If you cool the soup or stock in the fridge the fat will rise to the
top and congeal. You can then remove it easily and use it however you
like, either for flavor and 'mouth feel' in the soup, or as fat in the
matzoh balls.

> Can chicken fat be frozen and stored?

Yes.