It's interesting that Kodak spent many years of research into improving D76 but they were stuck because it had become a standard with clones from many other manufacturers. Initially a cine film developer the industry required it's availablity around the world. Later it became a mainstay of professional labs asa well. Kodak did alter the buffering and it's almost certain Ilford did the same.
The misnamed non Kodak D76H, (there was already a Kodak D76h MQ variant of D76), is really Haist alluding to the earlier 1927 Eastman Kodak Research Fine Grain developer.
It used to be common to publish some formulae as one part or alternative much longer lasting 2 part solutions with the alkali in Part B.
Sodium mmetabisulphite is used in some powdered developers to help protect the developing agents in powder or lquid form, this form should be used rather than the less powerful (antioxidant) form Sodium Bisulphite, it should also be reasonably fresh. It's used in a couple of Ilford powder developers.