Thanks for looking into that. I think the tickets sold is probably about right. I am not surprised by about 10,000 seats unsold (if your guesstimate is fairly close). The tickets are rather pricey (the cheapest seats are almost the same amount as what I paid per seat for season tickets). Maybe we see a late surge in Illini fans buying tickets, but I suspect they will get purchased through secondary market.
My cautiously optimistic guess is that you have QUITE a few fans (like Fighter and Mrs. Fighter) planning to attend but in no rush to buy tickets. If it doesn't sell out, you will likely have plenty of options on StubHub for very discounted seats with a good view. Hell, the other year we drove down for Braggin' Rights and made a whole event out of it, but we bought tickets on my phone an hour before the game from a bar, haha ... and we had awesome seats and got an amazing discount because of the weather. I would guess that we will see a surge of 3,000 to 4,000 if we lose at Rutgers and 5,000 to 6,000 if we win at Rutgers. Again, that is cautiously optimistic.
Back to the topic of the NU game's long-term standing, I want to be clear that I definitely accept the reality that NU will not want to move any home games away from their shiny new stadium. So, this was more a thought exercise of what would have been better in the past and what would still be better in a reality where NU would for some reason agree. However, I AM quite intrigued by the idea of having it be a bit of an Illini thing to just not play on Thanksgiving Weekend. It would solve the lame atmosphere problem, it would ensure that we have at least one more home game without awful weather most years and it sends kind of a message that we are not on board with fitting our "square" of a forced rivalry with NU into the "circle" that is the Big Ten's way overmarketed "Rivalry Weekend," haha. If we could get back to being a team that plays on Week Zero (we did in both 2021 and 2022), we would get three bye weeks and simply could use one on Thanksgiving Weekend ... HIGHLY doubt the TV execs would give a crap.

Using Florida State's cadence (they played Week Zero this year), our schedule this year could have looked something like this:
W0 - vs. Eastern Illinois
W1 - vs. Central Michigan (moved up, as I doubt KU agrees to play us Week 1)
W2 - vs. Kansas
W3 - BYE WEEK
W4 - at Nebraska
W5 - at Penn State
W6 - vs. Purdue (moved up a week)
W7 - vs. Michigan (moved up a week)
W8 - BYE WEEK
W9 - at Oregon
W10 - vs. Minnesota
W11 - vs. Michigan State
W12 - at Rutgers
W13 - vs. Northwestern (Wrigley) [this would be this coming Saturday]
W14 - BYE WEEK ... Illini relax and rest up for the B1G Championship Game
Again, ALL "outside-of-the-box" ideas are going to have pros and cons, and I can already hear the objections. I'm just saying, this is one way to address the SPECIFIC problem of the NU game always having an awful atmosphere.