We did ~2500miles in total. We gained a day as I drove from Oxford to Marseille in day 1 (22 hours with stops). But mostly spent 3-4 days in each country in a range of places. Getting food poisoning put me down in France for a few days on the coast and being the only driver it meant we stayed put for longer than we wanted.
From memory:
French coast = 3-4 days
Genoa/Milan/Monza/Lake Como 3 days
Alpes = 1 day (wish I spent more time here)
Austria = 1 day (wish I spent more time here)
Munich = 2 days
Stuttgart = 1 day
Black forest = 2 days
It was all fairly tight, but once you have reached that bottom coast everything is small distances (1-3 hours) away and doesn't feel far at all.
You say 3-4 days on the French coast, did you stay in the same place? Also, camping/hostels/hotels?