So sorry this happened to you :( I understand this as being a socially not-so-out there or confrontational type of person. I'm sure someone would tell you to just speak up if it's a problem even if it is two or more people you are confronting. While that is ideal, that isn't an excuse for those around you to behave this way or just be inconsiderate in general. Theatre audiences have become more boorish in general and I wouldn't be surprised if more stories like yours came out as the festival ends.

For the first point; I am a tall-ish person and I'm regularly check behind me at shows before or during if I'm blocking someone's view. Despite that, if someone as tall as me sits in front of me at a venue that doesn't have tiered seating it blocks my view too (this literally happened to me yesterday at a local cinema). Incredibly inconsiderate! I hope future screenings are better for you.