incorporated African grammar and some similar
vocabulary with slave English. Aks was one of these words.

Interesting. Just to ad spice to this stew, I have known two black Caribbeans (One from Belize, formerly British Honduras, and one from one of the former French islands) Neither of them said aks; rather, they said ahsk. Both of these places acquired their Africans as slaves, yet their pronunciations were distinctly British.
Might we conclude that cutural isolation had something to do with the development of aks?