#1 - welcome back! That was a lot of information packaged into a single post.
On the unfriendly interactions. On the Omaha Rez we preach over and over that it's about respect. When you go into their house, you need to respect the residents.
That is about the reaction I'd expect to cornering one or being where they need you not to be.
If it were me, I would go back and apologize. I know that will sound silly to some, but in my world it's the right thing to do. And I think it matters...
On the hitting your backpack or being touched while obviously nobody is around you is unusual, and can challenge your world view.
There are lots of instances like this on the Omaha Rez, and once I felt a touch on the back with nobody near me.
One of my friends said something came out of a tree, hit the ground running and brushed him as it went by. He only heard it and felt it, but never saw it.
He called it Counting Coup...
On the "invisible" thing and "preditor" mode. I've heard this too many times to write it off. Just don't ask me to explain how it could possibly be true.
I had an experience in Iowa last year that left me with the same feeling you have about it.... Can't shake it.
Again... Welcome Back...