Itinerary for now-- suggestions?

I think if it were me, I'd spend a day less in Venice and add it to Florence or Rome. That way you can go see some of the Tuscan country side and still hit up the main museums and other sites (assuming you're interested in all that). To me I guess Venice had less to see, though it was very pretty.

I think I found Pisa to be somewhat boring myself. I loved Siena though, which is a very easy day trip from Florence and it really is gorgeous.

Other than that I think things look good :) Enjoy your trip!

Where can I find the German rail planning website? I am now thinking about flying from Rome to Barcelona, would you recommend this?

I would fly Rome-Barcelona, because rail connections from Italy across southern Spain are abysmal....likely to take you an entire day to make the trip. Check whichbudget.com for discount airlines linking the two cities. I would also suggest arriving back in Paris the night before your return home and stay in an inexpensive hotel near CDG like the Ibis, Etap, or Formule 1 (accorhotels.com, use Roissy as your location). If there's any delay getting into Paris, you don't want to miss your flight to JFK. Either that, or book an "open jaws" flight into Paris and out of Barcelona. Most travel websites allow you to do this...look for "multi-city," "multiple destination," or similar options on their websites.