Wisconsin clinches with a win over Iowa.
If Wisconsin loses to Iowa that keeps Iowa and Northwestern (assuming they beat Purdue) alive. The problem, for both Iowa and Northwestern, is that they would need Wisconsin to lose their next two games to have a chance.
If Wisconsin finishes 7-2 or better they go to Indy either outright or by winning a 7-2 tie with NU based on H2H.
If Wisconsin loses out (vIA, vM, @MN) to finish 6-3 then:
Northwestern can win the division outright by winning out (vPU, vMN, @ILL) to finish 7-2.
Either Northwestern or the Iowa/Nebraska winner or both can finish tied with Wisconsin. Here is how those ties would be broken:
Wisconsin tied with Northwestern: Wisconsin wins, H2H.
Wisconsin tied with Nebraska: Wisconsin wins, H2H.
Wisconsin tied with Iowa: Iowa wins, H2H.
Wisconsin tied with Northwestern and Nebraska: Wisconsin wins, H2H2H.
Wisconsin tied with Northwestern and Iowa: Iowa wins, divisional record.
Note, therefore, that Nebraska, Purdue, Minnesota, and Illinois are eliminated.