Can I saw off broken freehub
I do not believe there are any from that era that don't take a 10mm wrench through the drive side.
The simple thing to do is remvoe the freehub with the 10, gently pry up the rubber seal on the back, note its direction, and shoot air/solvent/lube/oil/etc through it depending on what you've got and how bad it is, then finish with a heavier oil like Phil.
Edit: It indeed takes a 10mm allen.