Yes, I did read your initial post as though you only had 2½ weeks total for the eastern portion of your trip. My bad. With another week to play around with, you can certainly have a more relaxed first half of your trip than I was imagining, so everything you planned on is within the realm of reason. You can even add a bit more, although I wouldn't go overboard.
I would certainly add Memphis and the Blues Highway as I suggested earlier. Then look at some combination of Shenandoah National Park, the Blue Ridge Parkway, and Great Smoky Mountains National Park between Washington and Nashville (but not all three). And finally from New Orleans and Miami, your best Gulf Coast spots are included in Gulf Islands National Seashore. Remember that for the most part, the Gulf Coast tends to be swamp land although there are a number of small beach towns on US-98 between Pensacola and Apalachicola in Florida, while the Atlantic Coast of Florida tends to be very commercialized.
Your west coast leg is still a bit over-booked, and I would still caution you against trying to add too much to your east coast leg. Holidays are supposed to be relaxing, not frenetic dashes from one 'attraction' to another.