Shooting from the hip here, with limited knowledge of what has/will work for y'all, but here are a few thoughts about student attendance.
1) Start a student group of the most die-hard football fans and let them stake out a section for themselves in TCF (i.e. a block in the front X rows of the general admission section). Pick a name like Kill's Killers or Team Comes First (TCF) or whatever and let them pick out something to wear that sets them apart but still keeps with the maroon and gold colors of the rest of the students. It could be as simple as a special shirt, facepaint like warriors, helmets, whatever. They could also all bring towels to wave, bells, or some other prop. Make it unique to Minnesota. The group needs to make a pact among themselves to show up early and stay to the end and be rowdy. In exchange, they get special access to the team, perhaps a meet and greet or a special off season practice where they can play flag football with the team. Millennials like to belong to a group, and if this takes off, it would be something that other students wanted to take part in until it takes over the student section and creates a culture of supporting the team. Give this group a budget to make signs or flags like at ESPN College Gameday.
2) Encourage students to make up some of their own traditions and activities for during the game. Beyond wanting to be a part of a group, they want to be continually entertained. Here are a couple of examples from our baseball program. First, if we are down at the beginning of the eighth(?) inning, the announcer plays the Rocky theme song and a student from each section runs up to the top of the stairs like in the movie. When the train rolls by everyone puts up their fingers as a guess of how many engines the train will have. You guys have some of that stuff going already, but let students add to it so that they have things to do even if the game gets boring.
3) Make a challenge between the various Greek organizations or other campus organizations to sit together at the game in blocks with their letters/logo on their shirts and a sign for themselves. It can be a contest and a matter of pride for groups to be seen as the most loyal to their team, plus you are sitting with a group of friends for the game.
4) The University president and other well-liked figures should walk through the student section during the fourth quarter and shake hands and take pictures. Kids want a picture of themselves with the president or a former player for their Facebook or Twitter and may stay for that.
5) If you don't let the fans on the field after the game, consider doing so. After our games, everyone pours onto the field (after both teams have left) and fathers and sons or friends play catch with footballs while the postgame show appears on the screen.
6) Institute a rewards program sponsored by some local business where coupons are handed out as you leave, but only at the end of the game. Or, have a stamp card that gets stamped at the end of the game, and a person with all the stamps can enter into a drawing for a cool prize. It doesn't have to be elaborate, perhaps an autographed jersey or dinner with the coach.
7) Give students a way to participate in the game. For example, when the team returns after halftime, any senior student can line up by the tunnel to give the players a high five as they run out. Or, have the players come over to the student section after the game to sing the school song with students. Maybe even have them take off their jerseys and hand them to students if it's a commemorative type jersey game.
8) Make it a little more difficult to get student tickets. People don't always respect or care for things they didn't get through effort. When I want a ticket for a game here I have to go to the stadium ticket window at 6 a.m. on Monday morning and line up. I also pay $250 for my season tickets (as opposed to your $84) and another $250 for my wife's, plus a $35-50 per game non-student surcharge for her. You better believe I am staying for every minute of the game to get my money and time's worth.
9) Have some sort of contest where students can vote using their phones. Such as, what song should we play in the 4th quarter. Text Gopher1 if you want Zombie Nation...
10) Something has to be done about the tailgating scene right next to campus. Perhaps entice a local bar to set up a huge tent with margarita sales or put a cash bar in the alumni center with various other games projected all over. Set up grills that people can rent/use, or just put some tables and chairs out on the plaza with security who will watch people's coolers during the game. I don't know what the answer is to this one, but it needs to be a party before and after the game.
Finally, get a television contract that blocks out your games locally unless the stadium is at capacity. People shouldn't be able to watch the game at a bar a block away when there are seats to be had in the stadium for $13 each (that's what I paid on Saturday).