I'm creative enough to come
up with a solution myself, but some advice from the master is always apreciated.
There's not much advice
I can give in regards the ferret--cool little critters, ferrets I assume
you are increasing the familiars HP and attack
chance for it's part in adventuring success.
You might also increase
it's AC as it learns to move and dodge even
more quickly.
As an aside, I don't think you should ever allow a PC to gain more than one level from an adventure success.
Hope that served to answer your question.
Cheers.
gary