Hello Rosemary88
Holding the Swiss Travel Pass, this is your ticket for three days. No additional ticket is needed if you plan to take the Glacier Express during these three days.
The seat reservation can be made here:
https://shop.glacierexpress.ch/gex_en/specials/daytrips/glacier-express/?___from_store=gex_de
Please note, the Glacier Express is operated by the Rhaetian Railways, a partner rail company from SBB. If you have any questions concerning the Glacier Express, you may contact them by e-mail. I know from personal experience, their staff is very helpful (and the food on board the Glacier Express dining car is great, too!):
railservice@rhb.ch
The information about the dining car can be obtained from the timetable. You will find the fork & knife icon, which tells you that the train has a dining car. As a general saying, only Intercity trains (IC) and certain PE trains, such as the Glacier Express, do have a dining car.

Swiss public transport companies do offer complimentary travel assistance for people with disabilities. You may want to register yourself for the trip using the form made for this purpose:
https://service.swisspass.ch/handicap?lang=en
Also see this website: https://www.sbb.ch/en/travel-information/individual-needs/travelling-reduced-mobility/contact-center-handicap.html; the international phone number is also mentioned.
The Glacier Express uses the same tracks as the regular trains; thus, yes, it uses the official train stations.
This is a suitable itinerary:
If you want more connection time in Zurich, you could take the IR37 from Basel at 10:43, to arrive in Zurich at 11:52.

Let us know if you have got further queries.
Best wishes,
Roland