I disagree strongly (no offense).
Pushing and pulling is about sentience. Purely about the mind. Anything with one can be manipulated. With that much investiture, it's near impossible, but it could be done.
I don't have the precise wob, but I know it well cause a friend asked in response to a debate between me and another, here's the gist:
It seems quite unlikely that there is any major distinction between nightblood and a chalkling in ability to be manipulated other then massive investiture. If anything, he would be easier, due to his more human mind. (though actually that raises a whole other question of which is easier to manipulate, sentient or non-sentient beings...)
Anway, Egg, hope that answers your question!