Restoring a seriously damaged glass plate

Phase 2 and 3 of  the digital restoration of a
seriously damaged glass negative
from the 1910s.

This is my first attempt at a very severly damaged glass plate from Austria-Hungary around 1910.
The emulsion is washed down by water in the left hand side, and there is a sustained chemical stains, mainly from fixing mistakes on the right hand side. There are scratches, water strains, and possibly a worm's print on the glass plate that was found on the floor of a derelict attic in a Budapest house.
The theme is interesting: it depicts a steam donkey (steam-powered logging engine) with the machinist and peasants, women and children somewhere in Hungary.
With different masking, curve (tone and contrast) adjustment the theme is visible, however, the layers are smootly blended.
Any ideas how on to work with such a damaged plate are welcome.