My,
you do have a difficult undertaking there.
I am not sure that I understand why you want to invest this kind of effort in a dying technology, but I am sure you have your reasons.
Unfortunately my knowledge about fax and fax machines hooked up to a computer is limited.
I'd consider web based services, if it were only for the occasional fax here and there.
This is an example for a service that would send a fax:
http://www.freepopfax.com/
In addition, many email providers offer the option to receive faxes through the use of a designated phone number.
http://www.faxcompare.com/email-to-fax
As far as Puppy is concerned:
If your hardware supports it, I recommend Puppy 520 over most other versions of Puppy. It represents the forefront of development and has many convenient features earlier Puppies lack.
Many other versions are listed here
http://puppylinuxnews.org/releases/
Here is a forum for the very latest development:
http://www.murga-linux.com/puppy/vie...0f5f009dd42163
But in general: Puppy is a small and unique Linux, and a Linux one can get addicted to.
But it is not a big distro with a universe of repositories and programs. If you are looking for much further reaching possibilities, then there is probably no way around Ubuntu and its many derivatives and spin-offs.
Much success