Can I ask if the pass can be used on the 0549 train from glasgow to fort william?
Yes. As well as sleeper traffic it also serves as part of the regular service on that line, despite SERCOs attempts to avoid that requirement.
The train is marked as reservations compulsory but in practice it is not possible to acquire reservations for it if you are not going to/from England. It will not be full at Glasgow, in fact the loadings are often in single figures.
The stupid not before 09.15 weekday restriction on that ticket does not apply to the Glasgow-Fort William/Oban line as well as Inverness - Kyle/Wick/Thurso, Glasgow - Stranraer and services from Lockerbie.