This isn't quite true as it was "Michigan State Normal School" back then - founded exclusively to train teachers. All three directional Michigans are former normal schools. In fact, the MAC is stuffed with former normal schools. I believe the only MAC members not founded as normal schools are Buffalo, Miami and Ohio. Thread drift trivia.
Well, that always a judgement call when you have a predecessor institution. If it's just a name change, usually the founding date of the institution under the former name is considered the founding date. U of Michigan has a much more checkered early lineage moving from city to city with name changes along the way, but it still claims as its founding date the date of the predecessor institution. If you want to see one that's really complex look at the histories of the University of Kentucky and Transylvania University. It'll make your head spin! ;-)
In terms of MAC schools founded as normal schools, I think that you are correct with two exceptions. I don't believe either Toledo or Akron were founded as normal schools, though they may have had normal school divisions added at one point or another, as did Ohio. In fact, a bit of trivia: Did you know the only two colleges at Ohio University that were added by direct action of the state legislature: College of Education (Normal School, 1902) and the Heritage College of Osteopathic Medicine (College of Osteopathic Medicine, 1975).