That sounds reasonable to me. Cleon?
Hmm...
I'm leaning towards giving them the same ability scores. If we do go for different stats, I'd prefer a bigger difference - say give the Typhonic Beast the same physical stats as the Croc Mummy.
Let's say Str 25 and Dex 15. They should have a Strength at least a token point higher than a regular Str 24 Mummy, since they're Large. The Mental stats look fine, although I'd be tempted to drop Int to the standard 12, partly because I think they're more creatures of faith than intellect, but mostly to reduce the amount of skill-point juggling.
So, we've got.
Jackal: Str 23, Dex 17, Con —, Int 14, Wis 16, Cha 17
Typhonic: Str 25, Dex 17, Con —, Int 14, Wis 16, Cha 17
or
Jackal/Typhonic: Str 23, Dex 15, Con —, Int 14, Wis 16, Cha 17
or
Jackal/Typhonic: Str 25, Dex 15, Con —, Int 12, Wis 16, Cha 17or
or
Jackal: Str 25, Dex 15, Con —, Int 12, Wis 16, Cha 17
Typhonic: Str 27, Dex 13, Con —, Int 12, Wis 16, Cha 17