I thought the Jungfrau five day pass a couple of months ago without buying the Jungfraujoch tickets at a discount then Because I didn’t want to commit to a specific day without knowing the weather. Can I still get a discount if I buy the Jungfraujoch tickets tomorrow?
The usual recommendation is not buy tickets for Jungfraujoch in advance so yes if the Jungfrau Pass gives you a discount then you will get it buying on the day.
Yes, looks like you can buy a round trip from Kleine Scheidegg to the top for 74 CHF. Normally that would be 152 CHF.
Just show your pass when buying the tickets, and they'll apply the appropriate discount.
And I agree you did the right thing - you never want to book the expensive Jungfraujoch excursion in advance, because it's a huge waste of time and money if the weather's bad. Check the webcams before going up.