I know New Mexico St. is better than usual and Idaho sucks. But that doesn't help.
The Phill Steele power ratings for free on his web page have New Mexico St. as 1 pt superior and you have NMS at home so I would think a power rating might have them as a 3.5 pt favourite. I realize Phil has 9 sets of power ratings he uses to assist him in predicting these games incorrectly and this is just one set that he doesn't even use to make selections so it is only an attempt by me to put a bracket on what a game spread might be and I've seen the market different by up to 7 pts from it with no problem. But that is a small minority of the games.
The game also opened at 3.5 at Pinnacle so it seems reasonable to me that people who use power ratings, stat analysis etc. might come up with some value at -2.5.
This analysis should adjust for strength of schedule as I'm pretty sure Idaho has had a tougher schedule but should be in those numbers above. Your YPG analysis someone like Dr. Bob will adjust for the strength of the opposition etc. and see if Idaho really is this bad defensively apparently. Perhaps a more detailed analysis will reveal something.
If not that obviously the play looks stronger for you but with this type of money on Idaho clearly they smell the upset coming if you can call it that. Must be some other factor that they thnk matters here. A situation, an emotional factor in the game, a style of the teams that isn't reflected within season stats.
And of course my favourite but I have no idea here OL issues that are a weakness against another team's strength defensively disrupting an offense. Of course an injury here would be critical.
The reality is you may find out you want off your play. However, you also may find out this should be a 2% play. Good luck either way.