Well, when you're talking about something that not only doesn't but can't exist, it's difficult to make sense... Basically, even if Doc was to have memories of the events in 1955, he wouldn't have them in 1985 until after Marty makes the trip to the past, since technically THAT 1955 hadn't happened before then. Doc did have the note warning him of his own death from the "new" 1955, so he clearly did have memories of that timeline, but only after it happened. It's these little details that really start to solidify how impossible time travel really is. Except for our constant travel into the future, but that's just "time".

While I thought the show was a bit too frivolous in the beginning, it seemed to catch it's stride and season 2 was an absolute masterpiece. It seems like they went more for shock value in the first episodes over actual storytelling, but once they settled into good story and character development it got really good. Can't wait for season 3, although I certainly have been.