<"in thinking about this, i've come up with another question; if you have two bodies that total over 3 solar masses (but under 6 so each one does not "singularize" on its own) orbiting each other close and fast enough, what happens around the points on the edge of the system where the additive gravity of both bodies is greater than c?"

I'm thinking we're talking about neutron stars here right?

I'm not an astrophysicist but I think that first off, the radius of the neutron star is too big for this to ever happen, they would mechanically interact (touch/collide) first. And when this happens, god help anyone within hundreds of parsecs......

2nd such an arangement is NOT stable. Like an electromagnetic antenna that broadcasts more efficently at higher frequencies, a binary system of co-orbiting neutron stars broadcast gravity waves more efficently the closer (and faster) they get.

So they get closer, the system broadcasts energy and they get closer yet causing them to broadcast MORE energy.......

Greg Egan's book Diaspora has an example of the neutron stars colliding.