Being a medical student, I could only answer #1:
Bellevue and Tisch do have separate EDs. But residents rotate through both and the VA hospital next door. WOrd on the street is that tisch's ED kinda sucks: cramped. I walked through bellevue's ED several times and was blown away at how much space there is. It's not the ritz carlton but they have the fort covered pretty well. Runs like a well oiled machine from my outsider perspective.
Yes, bellevue is level 1 with high volume, public hospital, immigrants, spanish speaking, indigent, etc. I think there are only 3 other level 1s in manhattan.