[morzh]

I would not go for a stepless-variable supply using a tube as the regulator. It is an LDO equivalent in the tube world and will dissipate a lot across the regulating tube. Meaning, your current sourcing ability is severely limited.

I would use a tapped transformer. Better yet, and isolated variac (truly stepless-variable). Then rectify and filter.
And then use a couple of smaller transformers for the filament volatges.