OMG-newbee. This is Austria, safe as hell-in general.

ALL stations have waiting rooms, lounges (in the strict meaning) are only for those holding special hi-price ´status´tickets and if they are (I guess not, Austria/OeBB does have them, but mostly only in provincial capitals) then these will be closed night time.

I kind of guess you have scored a cheap0 flite0 on that dreaded RYAN from Trv-you have to use the citybus there and buy ticket before. There will be other ways to reach it from Z-via Trieste-Venezia (inland=Mestre), but that needs more changes and is not to do in nighttime.

Also note that the 2nd train Austria-IT needs you to REServe. Its an overnight coming partly from Wien so you could also check an earlier boarding place and go there-lengthens the travel time, more chance to see. LIke via Maribor-into Austria-Graz-board it at Bruck/mur. Thats the nice things of these passes-you do not blindly have to follow these planners giving fastest route and make detours.