Milwaukee and Baltimore are the other two, yes.
Interesting that you are so keen on Jacksonville. It has always been good but I don't think it holds a candle to any of Hopkins' Boston recordings from '77.
Detroit and Toronto '77 are both JEMS masters as you deduced and yes, the same guy yelling on Saginaw is yelling on Toronto. That's where he lived. He came down for the '78 Saginaw show from Canada.
Certainly a big chunk of our '70s boards came via Sciaky. But I don't believe the '77 shows were from him. As I wrote before, the tapes surfaced in the '90s. First person I knew who had them and told me the story was LA-based.
Finally, I can assure you that Charles Cross and Lynn Elder are not the same person, dress or no dress. They were not written by Mr. Cross.