The Stats are fine except Con we have him at 67, also, we increased his inherent armor to 18. Oh, based on our 1st Ed DMG, his strength would be closer to 12. His damage is only a 1d6 and his power or rot, mind control etc makes up for his weak Str.
Also looking at the ultimate Game of horror, CoC, and the fact Demogorgon is kinda a god like Bast,Nodens etc, the other stats are fine, in our opinion, but skills could be a little higher. Dodge could be higher so he can dodge more than one opponent , and specific skills could be upped. But we try to watch out for the dnd power creep. We also sometimes allow supernatural beings a regeneration roll, sometimes.
Hope it helps. But as you posted, he is very usable.