Larochette is less than half way so you have plenty of scope to do some wiggly bits along the France-Belgium-Lux border once south of the E42. Use the maps at
http://www.viamichelin.co.uk/ to determine the good roads (as with the paper maps, look for the green worm alongside the road for scenic routes)
Day 2 is a longer day of over 300 miles even by the shortest route. If you take the highly recommended Route des Cretes as mentioned above then you are in for a long day of 350 miles with some sections where your average speed will be quite low.
Personally, I'd add an extra night to the journey and stay with a friend who lives near Mulhouse. Then I could enjoy an afternoon in the Vosges and the following day in the lovely mountains between Dagmersellen & Interlaken such as the excellent
http://en.wikipedia.org/wiki/Glaubenbielen_Pass
If you really only have one day after your stop in Larochette then get on the free German Autobahn to the Swiss border and find your way to Dagmersellen then have a play in the mountains in the latter part of the day.