I'm sure that you are right that Ohio will not be in the MACC if they end up 6-2, but I disagree with one part of your post.
After research, we need WMU to beat BG....
If Ohio can get to 7-1, Ohio goes to the MACC game. The following are all possible:
1. Everyone else could falter, and Ohio could face some 6-2 team
2. BG could defeat WMU and Miami, then Ohio could face a 7-1 BG team
3. WMU could defeat BG, and BG could defeat Miami, and Ohio could face a 7-1 WMU team
4. Miami could beat BG, in which case Ohio could face a 7-1 Miami team. In this case, it doesn't matter if WMU also finishes 7-1 as Ohio would eliminate WMU via the tiebreaker.