If you look around you'll find that at least one person has done route 40 from Phila into Baltimore. The only problem is that there is a bridge that you'll have to hitch a ride for (no bikes allowed).

Route 40 is busy but has a wide shoulder along most of it going into Baltimore from the north. There are relatively new "share the road' signs-- motorists are somewhat accustomed to seeing cyclists on 40.

Philadelphia to Baltimore along (mostly) route 40 is 100 miles, I suppose that extending that to NYC will stretch the ride into something that is easily doable in 2 days by decently prepared cyclists.