Fix loose screw in sofa leg
Well, I was able to get it to hold in place by wrapping the screw in a decent amount of packing tape. Seems like it's holding well, and of course as long as the screw is fastened the leg will do the rest of the work. 

Still, I am definitely open to better band-aid solutions or what a proper fix would look like (i.e. would I need to weld it?).