You say there is no evidence for the connection with Shechem. I said
that the association with Joseph is itself evidence, but you ignored
this. More specifically, the context concerns the political ascendancy
of Ephraim.
Other evidence can be adduced if one accepts that the texts were written
by different authors. You give a lot of weight to the requirement of
consistency with other texts about Jacob. It would be more convincing if
there were another text about Jacob's military activities.
But in any case I don't believe that the text in question is primarily
historical. We are dealing with personifications of the political
realities of a certain era -- an era, I would guess, in which Schechem
was still pre-eminent, and there was a memory of its pre-Israelite status.