Definitely too many places, but to help us suggest where you might cut, please tell us what sorts of things you want to see and do during your time away from Kandern--and is that 17 nights, or will some of your time be spent in Kandern?
Is "we" an adult couple, or are there children involved as well? If so, what are their ages?
I'll start with a couple of places I visited in 2015:
For me Dresden is pretty much all about the museums. The city was heavily targeted during the war, and only a fairly small part of the oldest area has been rebuilt in the historic style. There are better options if you aren't interested in the museums, and if you are, I think Dresden needs more than one full day.
Berlin is huge, sprawling and stuffed with museums and historic sights that can keep a visitor busy for a week or more. Unless you go out to Potsdam, the architecture isn't what we tend to think of as "old Germany". It's not the sort of place I'd want to go for just a day or so. If you are museum-lovers, or if you want to take in a lot of the historical sights, I'd say four nights is a minimum time for Berlin.
I suspect that dealing with a car will be a challenge in some of the larger places on your list, with high parking fees if you choose centrally located lodgings that are convenient for sightseeing, but that's something you can re-visit when your itinerary is a bit firmer.