can't help on removal (some have suggested various products but i haven't tried any). But, after wash down i wipe the windows with an Absorber. has prevented water spots so far. good luck, ron
Polish with a cutting compound. Or use bronze wool. Won't leave pieces behind to rust like steel wool. I this doesn't work your glass is etched so you need to live with it or replace it.
Lot’s of snake oils out there for water spot removal. As mentioned it may be etched therefore could need to try mechanically (polishing) or hire a professional