Really great post! I too am very surprised at how some people see and interpret Luke in particular. When the movie had recently come out, one of the Freaks here insisted that Luke was "humiliated" by having to drink the sea cow milk. I didn't remember fully at the time since I had only seen it once, but I responded that I didn't remember that scene as humiliating at all--that it was Luke almost taunting and purposely trying to disgust Rey with his drinking the milk, and further showing how in tune and balanced he had become with the island. Seeing it again on Blu Ray (and the gif that pops up every once in a while), it's definitely Luke trying to disgust Rey so she'll stop following him and bothering him. I don't remember who it was I had the exchange with, but I wonder if he still feels the same.
I agree, that Luke was both testing Rey during the combat sequence, and intentionally trying to disgust her during the milk drinking scene. However, what bothers me about the depiction of Luke is that he's embraced pacifism, seclusion and withdrawal because he feels that intervention as a Jedi would mean hubris, and a sort of domination. Luke's competence with the Force, as power, is portrayed as somehow unjust or destructive.
Take the milk drinking scene. It's very "punk rock", in the sense that Luke's almost begging Rey to "kill her idol". Remove him from the pedestal she's placed him on. I find the scene annoying in the same way I find punk rock annoying: By glorifying poverty squalor etc, you make a virtue of your deplorable circumstances. I once knew a guy who was wealthy, had a trust fund, but went dumpster diving for food as a "freegan" back in the 90's. Luke is a kind of Jedi Freegan. His pacifism and minimalism aren't meant to be absurd, because they reflect the absurd philosophy of the director. We're meant to admire Luke for his "restraint".
When people criticize Luke for being weak, they're right. His weakness has less to do with his ability, than his philosophy. He's a capable Jedi, made pathetic by his ideals. Does that not encapsulate the frustration people have with the film?