Around 2040 EST We viewed an irregularly flashing object flying from WSW to NNE (roughly) from Jacksonville FL. Is the SpaceX 2nd stage still up there and if so, would it be tumbling and visible? Is there somewhere I can go to see where there are known tumbling satellites?
You wouldn't see a 2nd stage tumbling and visible. Odds are pretty high that what you saw was some kind of an aircraft. The best site to see visible satellites, or at least the one that I use, is http://heavens-above.com/