Don’t be too worried about moving to Chicago – there are plenty of tracks within a few hours. Brodhead, WI is just over the border near Rockford. Wisconsin also had Dousman, Stockholm, and the Briggs Motorplex at Road America. Illinois has Norway (I’d guess about 2 hours from Chicago) and Quincy, and long track events at Blackhawk Farms near Rockford. If that’s not enough, there’s even more in Indiana, and MRP, Grattan and Gingerman (the last 2 are long tracks) in southwest Michigan. So if anything, you’ll have too many choices. Not sure which of all of these run Rotaxes, though – remember, Wisconsin is the home of Briggs and Kohler, so there’s probably more Rototiller classes than Rotaxes (Brodhead only has KT100’s and HPVs for 2 strokes, for example).
I’d say keep the kart – you’ll probably need it to keep your sanity in grad school.