Point to Point Rail or Rail Pass

For those few trips, just buy normal tickets. You have only one trip in Germany, so definately a normal ticket for that (advance purchase is cheaper in Germany).
Are you planning on using any mountain railways during your stay in Mürren. If yes, you may want to consider a Swiss half price card, you will have to do the arithmetic yourself.
You can look up Swiss times and prices on the SBB (Swiss Railways) website: http://www.sbb.ch/en/home.html

But, where are you going after Freudenstadt? I had to look it up, Freudenstadt is a town in Baden-Württemberg, near Offenburg.

See this webpage for more info: http://www.seat61.com/Railpass-and-Eurail-pass-guide.htm

Thanks for the information. From Freudenstadt we are going to Rothenburg then on to Bacharach, St. Goar then to Kobern-Gondolf where we will meet friends who have a car for the rest of our trip in Germany. Any recommendations on rail travel would be appreciated!

One thing about the SBB website: It assumes that you have a half-fare card, so the fares it displays include the 50% reduction. Keep that in mind when you do the math to see whether the half-fare card will pay off for you.

And do investigate the individual deals often available on tickets within Germany.

The Swiss pass products cover (or at least discount) all public transportation in the country, which is why just counting the train rides above is probably not a good reflection of what you'll really use. For about $125 per person, the one-month Half-Fare Card saves money if you would spend $250 at full fare. www.jungfrau.ch will show you ticket prices around the Berner Oberland in chart form – click on English, then Travel Information. Also on that page, follow the map link for a view of discounted lines with different pass types.

With the few trips you'll be making, I'd probably just buy P-P tickets. However if you want to confirm which option is the better deal, you'll need to do some number crunching. Add up the cost of P-P tickets and compare that to the cost of using either a full pass or a half-fare pass.

You'll need to include any excursions you'll be making during your visit to Mürren (ie: Cable Car to the Schilthorn, trip to the Jungfraujoch). If you'll be doing a lot of exploring in that area, the Berner Oberland or Jungfrau Regional passes may save you some money.

If you haven't been in the Berner Oberland before, are you familiar with the route you'll be taking to get from Interlaken to Mürren (there are two options).