I have a tip to share about lessening tension of the wiper on the windshield caused by modern reproduction wiper arms<which have very strong springs.
If you look at Otto's picture, you will see 2 holes in a tab where the spring eye goes through one of them.
You can drill another hole in that tab at the very end of it for the spring eye, reducing the pressure on the windshield enough for smoother operation, without losing contact of the wiper blade on the glass.
I don't have a solution for the OP's problem without a picture of the inner workings of his wiper arm.
