space maintainers are as you correctly said to keep the space for an adult tooth if a baby tooth is prematurely extracted. however if you are going to college are you sure there is even a tooth coming in? if you have had the space maintainer in for 2 years i doubt it is doing what it supposed to be doing as you've most likely grown in the last two years.
the band around the tooth is connected to a metal bar that should contact another tooth. if it isn't contacting another tooth, it isn't doing squat for you anymore
bands are good at collecting food, but if you are religious about cleaning it i wouldn't get too worried about it.
if your space maintainer is working as it is supposed to be, there should be a permanent tooth already in (unless you are very very very delayed) which i doubt. you may be just missing that tooth and should consider an implant or bridge or some other restorative option to prevent tipping, super eruption etc.