questions:

1) Do non warriors parry with their weapons (athame daggers, cudgels) if they have the skill in Combat? If yes, then what is the weapon for each guild?
2) Does it stack with shield parry?
3) Does a BM/BC parry half as effectively if only wielding one weapon for whatever reason?
4) If so, assuming a two hander parries as effectively as a two-weapon wielder, does that mean a two hander parries twice as effectively with one two handed weapon than a person does with a one handed weapon?
5) What stops a person for parrying? I know being sprawled does, what about paralysis? entangled?

Yes, we can parry with cudgel/staff/athame. Bards can't parry with their instruments, which aren't weapons. Yes, it stacks with shieldparry.

So I assume you can symbol parry too?

When you weaponprobe a symbol, does it have weapon stats? If it does, then yes, otherwise, no.