I think you've got a nice trip laid out, not overly rushed and still with plenty to do. I will simply offer a couple of random observations...
While you can certainly make it from Lancaster to Cleveland in a single day's drive, and there is plenty to do in Cleveland starting with
Cuyahoga Valley National Park and the
Rock and Roll Hall of Fame, you seem to have time for those already built into your itinerary. What I'd suggest then, if you want to take two days to Cleveland, that you eschew the Pennsylvania Turnpike through Pittsburgh and instead head up the
Susquehanna River Valley on US-15 to
US-6 and take that west into Cleveland.
The other thought has to do with ferries, of which I'm a big fan. The Cape May-Lewes Ferry is one of only two ferries that are part of the US highway system as it carries US-9 from New Jersey (where it's signed as a north/south road) to Delaware (where it's signed as an east/west road). Oddly enough the only other US highway that involves a ferry is the next in numerical order, US-10, which involves a ferry across Lake Michigan. There are also a couple of smaller ferries on or near your route that you might enjoy: the
Woodland Ferry in Delaware and the
Green River Ferry in Kentucky. Both of them are free!
AZBuck