Pass vs normal tickets?

Only you can decide, but don’t forget that one major benefit of the pass is flexibility. I’m guessing some of those prices you’ve found are for restrictive tickets where you have to commit in advance.

Apart from the Thalys from Paris-Amsterdam, and the Nightjet, I don’t see any need to reserve ahead of time for the rest of your trip. So it allows more spontaneity if that’s important/

I’m not sure what you’d be reserving on Interlaken to Chur. No reservation needed. Paris - Amsterdam would be €30 reservation.

All the details have already been written I'd say.

You could use your pass on Freiburg - Interlaken day as you don't need it on 03/06 (Jungfrau). I'd recommend not to book Jungfraujoch in advance as if the weather is bad, you won't see anything and lose 178€. Tickets can't sell out.

If Freiburg is not a must, I'd really recommend Basel instead, it is a much more charming city. :)

- Freiburg/Basel - Interlaken : I'd make a few hours stop in Bern and then take the boat between Thun and Interlaken if you've got time

No reservations necessary in Switzerland. I guess you're taking the reservation-free coaches on the Bernina Express.

You could consider a 1st class 5-day Eurail Pass, not that much more expensive.

Edit : Don't know where you've got the 80€ ticket price for Thalys, it is 149€ for that day. As 29/05 is the last day of a holiday weekend, I'd really recommend on buying that seat reservation ASAP. A Eurail Pass is even more worth it ! Though there are only 2nd class seat reservations available, except if you take the 19:25 train out of Paris

Interlaken - Chur : longer but more scenic route (there are engineering works on the "boring" route via Zurich anyway)

- Interlaken Ost - Lucerne 2h  Interlaken-Luzern Express

- Lucerne - Pfäffikon SZ 1h15 Voralpen-Express

- Pfäffikon SZ - Chur 1h

As it is reservation-free, you could suddenly decide to spend a few hours in Lucerne !