More on New Englan in the Fall
First some comments on your routing. I think that the drive to the top of Mt. Washington is well worth the time, but if you do this, then it's probably not worth backtracking all the way to Conway to cross the White Mountains by way of the Kankamagus Highway (NH-112), especially as this would require that you drive through North Conway twice (ughh!) You're probably better off only coming back down NH-16 as far as US-302 and taking that up through Crawford Notch to the west. Enjoy both the state park in the notch and the lovely town of Bethlehem at the junction with US-3.
Between Burlington and Deerfield, you have a choice of two basic routes. You can stick to the Interstates (I-89 and I-91) or you can use VT-100 from Waterbury to Wilmington before cutting over to I-91 to complete the journey. I highly recommend VT-100. It is the quintessential New England two lane blacktop through some of the most charming towns in the region. It will take considerably longer than the big roads, but New England in the fall should not (indeed, given the number of leaf peepers, cannot) be about speed runs.
Secondly, some lesser known, but worthwhile stops. Others have hit most of the high spots. Your choice of Boothbay Harbor as a place to see the rock-ribbed coast of Maine is a good one, but be sure to continue on down the peninsula via ME-27 and ME-238 to Newagen to see it all. Another worthwhile stop is the town of Plymouth, VT. The attraction here is that this was the hometown of Calvin Coolidge, and the entire town is now an historic park, frozen in time in the 20's. It is just the place to take a New England Fall walk.
AZBuck