Yes, by "wing nut" I mean the bolt on the right side opposite the quick release lever. I unscrewed it from the axle and discovered that the plastic over the actual bolt was cracked -preventing it from tightening. I replaced it with a "wing nut" from an old wheel and it now tightens properly. Although I won't know until tomorrow's ride, I suspect the rubbing issue will be fixed as well.

Thanks everyone. Obviously I have a lot to learn about bike mechanics but you guys are helping.