I guess I had a couple thinks I would thing through before making the move.
First, I think I would research if there was anywhere that was a semi-reasonable drive to get our BSN (Sioux Falls, Sioux City, Marshall, MN?)
Second, I would not expect moving your oldest child would be smooth. Rural Iowans are not real mobile creatures and high school kids are going to have their friendships pretty well established. Even if they are not outwardly mean they might not be super welcoming either.
Third, Are you sure your "forever" house will be that inexpensive? I would go and look firsthand at some places next time you visit. We are currently looking at places in the small town DH and I both work in and many are very reasonable, but the inventory is finite and lots of them have something glaringly unappealing about them even if they are mostly cute and solid little house.
Fourth, will your Dh be happy either SAHP or working very part-time?