Hi, your trip is looking nicer with every change
I didn't find information on what time of year you plan your trip. In Switzerland that's important of course.
If you consider Day 5 to be a travel day, this will be rather light. Or do you plan to walk around in Fribourg ? Indeed a nice town, but not really a must-see in my personal view. As an alternative, if you manage to get the luggage to Interlaken, get off the train in Thun, take a boat on the Thunersee, make a stop at Oberhofen Castle (forget the castle, visit the gardens) and continue on the boat all the way to Interlaken. In Interlaken I presume you'll go to Grindelwald and take the Jungfrau express train ? Not cheap but worthwhile. You could also (or as an alternative) mount in Grindelwald on the First gondola line. I don't know if you really need day 6 and 7 both in Interlaken if you used day 6 for the Grindelwald trip. You could choose to use 7 for the Aletsch area. Spend a night in the Riederalp or Bettmleralp area, and don't forget to go all the way up to the Eggishorn to see the Aletsch !