Sam: Washing before Kiddush does have a source, the Rema. I would like to believe he understood the Gemarra pretty well. I’m not sure why the Eastern Ashkenazi poskim started going against the Rema here.
Joseph: I imagine the 3 hour custom exists independently of that typo. One theory is that 3 hours is a chumrah(!) on the previous 1 hour German custom.
I’m curious as to the actual demographics of people waiting 3 hours. From being around the block, it seems like the people who are just doing it out of minhag lazy far outnumber the people doing it because of an established yekkish tradition.