Actually, it seems to me that you missed the point of the comment. If “form of a slave” is not to be taken literally, then it is difficult to take “in the form of God” literally—or at least as being a statement of identity with God. The difference in construction is accounted for by the fact that a shift is made from one state to another. Once Jesus has taken the form of a slave, he is “in the form of a slave”.
I have yet to see any evidence that “being in the form of God” would have been understood as a way of say “being God”.
There is very little scholarly support, as far as I can see, even among conservatives, for the translation of heauton ekenōsen as “emptied himself” of something such as divinity”. The idiom means something much closer to “poured himself out” or “made himself of no account”.
I still think the passage makes best sense as a anti-imperial “hymn”. Jesus does not act like the pagan ruler who makes himself equal to God but takes quite the opposite course, to the point of a degrading death on the cross, but as a result of this obedience he is given authority to rule and YHWH is glorified among the nations.
I’m afraid I don’t have time at the moment to address the other questions.