NIU is 1-3 in the MAC facing a Western team that is 4-0 in conference place. WMU is the home team yet NIU is still favored. Does this seem odd?
Well I agree with NIU being favored here. The difference is defense, and WMU doesn't play much of it.
When looking at MAC games only, NIU is #1 is yards allowed per game and #2 in yards allowed per play. WMU is 8th out of 12 teams in both yards per play allowed and per game. Although the WMU's offense is better. They have also faced a weaker schedule within the conference and I see this as a bad matchup for them. Both NIU and Western Michigan have faced Buffalo and Ball State in MAC play this season, but the Huskies other two conference games were against Bowling Green and Toledo, where the Broncos faced Akron and Kent at home. BG and Toledo are power rated as #2 and #3 overall in the MAC, and Akron and Kent are 11th and 12th.
NIU is 27th nationally in defensive efficiency, and WMU is 120th. I will ride with the better defense here.

1.5% on NIU to win outright, let's take the points out of it.