> He mistook that as an invitation and told us he'd be happy to accompany us on our drive back to her place if we would take him on a tour and show him around the beautiful landscape.

Bro he was 100% conscious of what he was doing. No real friend would do the third wheel like that. He was hitting on your girl on moment 1 and you got played like a flute. You also never stood up except when you tried to kill everyone in a car accident?

Thank god you are now getting mental help. Learn to take care of yourself. Learn to stand up for yourself. Learn that no friends is always better than friends who manipulate you.

Also about that "they are now happily together"

1. you shouldn't care. Move on. You will find better friends and a better girlfriend if you learn to value yoursef

2. they won't be happy. She has clearly big mental issues and she's doing nothing to solve them. He sounds like a psychopath, he watched you jump off a building doing nothing? Just to get a girl? He can't make genuine bonds with people, he lacks the empathy for that. Keep him away from your life no matter what, it can only end badly.