Mmmmm I’m not sure which pass fits you best since 66 days is more than 2 months. A 3 months pass would be quite expensive.
I guess it’s a writing mistake but Tirano and Torino are not anywhere near each other.
Interlaken - Barcelona will be quite hard to achieve in a day due to the incredibly bad high-speed connections between France and Spain. There’s a good daily connection but it includes the Lyon - Barcelona AVE : at the moment you cannot get Eurail reservations online for it. My advice would be to buy reservations when you arrive in Barcelona, it shouldn’t be an issue.
If the final journey from Interlaken to Barcelona only serves to take the plane back at Barcelona, then look into an open-jaw return so you can fly into Barcelona and fly out of somewhere closer to Interlaken. That is not necessarily much more expensive than a normal return.
Might it be an idea to remove Barcelona-Paris from the pass itinerary?
That might bring the trip under 2 months, and avoid the cost and hassle of buying reservations. Just pay cash for this journey.
The same could be true of the final leg to Barcelona
I’d agree with buying a regular ticket for Barcelona - Paris. This heavily depends on your travel dates though : you’ll have to book months in advance to avoid 200€ tickets.
Since you’re moving quite a lot a 2 months continuous pass looks like a good deal : you don’t have to think about whether it’s a good idea to use a pass day, etc.
There is currently a 25% discount on passes but you must activate the pass on 1st June at the latest.
Only be aware of mandatory reservations throughout your journey, some need to be booked well in advance (thinking of Paris - London - Brussels especially). More info : https://www.seat61.com/interrail-and-eurail-reservations.htm
Interlaken Ost - Lauterbrunnen, Grindelwald and above is not covered by Eurail but you get a 25% discount. On the other hand boats on Lake Thun and Brienz are fully included !
25-50% discount as well on multiple mountain railway and boat operators in Switzerland. Check :
https://benefitsportal.eurail.com/benefits/swiss-private-trains-benefits/
https://benefitsportal.eurail.com/benefits/swiss-private-boat-benefits/
