Although the chess.com engine prefers Nxa6, I'm pretty sure that black wins quicker after 2. ...ba and therefore that is the stronger capture for black.
We'll find out when @tygxc solves chess.
Um, sorry scratch that - he's not going to solve that bit.
Ke7 is very probably a blunder, except technically in the unlikely (but not logically impossible) case that the Ba6 sacrifice is winning. Even I find it difficult to be pedantic about this, but I am epistemologically obliged to be.
In your personal interpretation of epistemological obligation. If it is your belief that there's genuine doubt about the outcome of 2. Ba6, then of course it follows.