Ahh, how did I know you'd say something like that. Do I find it insulting? Nah, at this point it's just funny. Pathetic, but funny.
What does that have to do with anything? That curtain just separates the sections within the cabin. Irrelevant and immaterial. (Actually, curtains are material, so...)
Surely you've been on a commercial flight? Those window blinds can be opened or closed at will by whoever is in that seat. They were all closed on the tarmac at Seatac so no potential sharpshooter could see where he was? But once they were airborne he could have opened any of them that he wanted to look out of.
They discussed it amongst themselves, not with Cooper. But they didn't head for the coast, so the question will forever remain unanswered if Cooper would have objected.
I think this is everyone else's question to you.
Nobody knows or ever will know what Cooper's plan was. But Kam's theory is as good as anyone's. You say it doesn't fit the evidence. But the evidence is, what he describes is precisely what happened. If... IF Cooper wanted to jump where he did, south is all he needs. South IS a path. Mexico is south. LA and SF are not. Reno is. They did not head for the coast. They went south, and Cooper jumped where he did. Again, no one will ever know whether that was his intent. But if it was, it worked.