"For the present, if we can, let us limit our discussion to the Petrine primacy. If, for the sake of argument, we were to stipulate that the theological differences were minor and of non-essential matter, could the Orthodox come into union with Rome while she reiterated the claims made by Leo and other early pope?"
In haste as I am at the office; this is precisely what the Orthodox/Roman dialog recently resumed is discussing. The sentiment seems to be that if a working definition of papal primacy can be arrived at which is acceptable all around, the other issues will fall into place. Personally, I think the writings of the Fathers and the Popes from the early years of The Church as well as an in depth study of how whatever primacy The Church actually recognized in the popes worked out "on the ground, then", as opposed to the post hoc, propter hoc reasoning which seems to infest so much of this discussion from both sides, will be vital to any final resolution of this fundamental question. Even that will be difficult because it is not only possible, but likely, that each "side" thought the other understood what it was saying even then, when in fact neither side understood the other after say, the late 500s or early 600s.
As long as the West maintains that "first" means "superior" we will not even be able to come to an agreement to convene an Ecumenical Council, let alone hash out theological differences.