The info about Madara talking about his past is all you need cuz that's when he talks about when he encountered the 1st. You didn't have to take anything literally. It was all in the manga for you. Here's the pages you want to look at.
I won't get in to what MS techniques Madara had since I don't believe he had the same techniques as Itachi and Sasuke. But if he did have the same MS techniques as them, then at least for Amaterasu, the 1st could just use his Wood element or even Earth element to defend against that. Wouldn't know how the 1st got around Susano though unless he just waited until Madara exhausted his chakra.
I know the purpose of this thread. I even put the circumstances of the fight in a realistic (albeit, a very simplified) perspective. Also, I don't think anybody in this thread is doubting that the 1st won back then....