I feel like an alien species observing humans. I can do all the things to fit in but I don't understand them...

People do these things you mentioned, for example positive gestures, to reassure eachother that they are part of the same team and understand social cues and unspoken norms. Its a system that evolved to weed out weirdos like you who either cant or wont play by the rules.

Yes! I too am autistic!

*you're