A few points:
You cannot add strength mod to AP for a weapon with a base AP of 0.
Bite attacks are usually an animal's secondary attack. This means they have a lower attack bonus, rarely can be used more than once in a round and only as part of a full attack, have a smaller damage die, and can only apply 1/2 their Str mod to damage. So feel free to give them a high AP as it isn't nearly as bad as it looks.
Gore, bite, rend and possibly hoof attacks should have AP. I like using the values suggested by Prof.Dogg: Medium have AP 6, Large AP 9 and Huge AP 12, small and smaller creatures don't get AP. Use these values as the toatal, in other words don't add Str on top of them, based on the theory that different animals may have a lower Str but better base AP so it is easier to just go by size. "Dire" creatures, such as the sabertooth, should have a damage die and AP of one size category larger so you may want to give your were-animals values for a large creature.
Hope that helps.