I don’t mean this as an insult, but is this your first time in Europe proper? I ask this because you are still being very idealistic about what you can accomplish on a two week vacation. (You didn’t say how long this is going to be, so I’m guesstimating)

Let’s just look at your Berlin/Munich/Salzburg/Fussen portion for a second. It will take you 6-7 hours to go from Berlin to Munich. It is 3-4 hours from Munich to Salzburg roundtrip. It is 6 hours from Munich-Fussen roundtrip, assuming that you catch the bus right off the train. That’s 15-17 hours of seeing Germany/Austria from a train window. Then, factor in your time that will be spent using public transport in each city. (Namely Berlin and Munich as it’s generally better not to drive there) That will easily bump you to the 24 hour mark. Figure that you will sleep 7 hours per night. On 12 nights, That’s an additional 84 hours there. Plus, you won’t see anything of value on your last day and at least half of your first day. Assuming that you don’t nap due to jetlag, that accounts for another 24 hours.

So, on sleep, travel and transportation alone, you are already down 125 hours, or 5.2 days and you haven’t seen anything, eaten a meal, walked around to explore the city, explored other areas of interest by car or train or gotten to/from Dusseldorf for your two flights. Yes, there are ways to cut this number down a bit like renting a car in some places or taking an overnight train. But, figure on 5-6 days being collateral damage on a 2 week trip. 4-5 cities would be my max over 12 nights.