I'm not sure what you mean about exploring Munich by train. Can you clarify?
That question aside, it appears that your trips looks something like this:
Travel by car to Munich; drop car.
Sightsee in Munich.
Public transportation to Luzern. Side trips??
Public transportation to Interlaken. Probable mountain side trips.
Public transportation to Lugano.
Public transportation to Cinque Terre.
Public transporation to Rome.
If I have that right, you have not much train/bus travel in Germany, just the Munich-to-border leg of the trip to Lucerne, though this seems to involve a Munich-Zurich bus, all of which trip I guess you'd need to pay for (I'm unsure about the part from the Swiss border onward). So I think getting a rail pass that includes Germany will not be cost-effective. This is especially true if you're sure of the timing and are willing to buy that ticket now. (I'm sure someone will correct me if I'm wrong.)
You're spending enough time in Switzerland, and the marvelously-engineered Swiss trains are expensive enough, that you'll probably benefit from some sort of Swiss transit pass. You should start by listing the trips you plan to take within Switzerland (the definites and, separately, the maybes). Check prices on the SBB website, being aware that the initially displayed prices assume that you hold a half-fare card. Choose a departure and change the pull-down box on the next screen to "No Reduction" to see the full fare. With that information you can figure out whether the half-fare card is a good option or whether the Berner Oberland Pass or Swiss Travel Pass would be better. Understand that the various passes vary with respect to how much coverage they give, especially for mountain transportation.
It's true that Italian trains are inexpensive enough that rail passes usually do not pay off in that country. You have just two trips planned, so point-to-point seems the way to go. You can save money by buying the fast-train legs of those two trips in advance. Check schedules and fares on the TrenItalia website.
