Adventure Cycling's Atlantic Coast route will get you all of those states except DE, RI and WV. It skirts Philadelphia (Where I live) without going into the city itself. Maybe use that as a base and modify it. BTW...DE is somewhat of a pain unless you just want to dip into the northern end from PA and then come back out. Once you get further south you have to deal with getting across the Chesapeake Bay to MD.

If you really want to hit DE, you could ride from Philly to Cape May, NJ and take a nice ferry ride to Lewes, DE. There is a great state park there (Cape Henlopen) with camping. You would probably have to hit it during a weekday because I think the campground is usually booked months and months in advance, at least on the weekends. You can check the park's web site to see.

Just about everywhere in western MA is going to have hills, and some steep ones. NW CT is also very hilly. Last September I did a week tour from Brattleboro, VT to Philly that had some stiff climbing a couple of days. Hit VT, MA, CT, NY, NJ and PA.

Agree that Pittsburgh is a logical place to catch the train back to CHI. Carry-On bike service on the Capitol Limited will require a reservation.