There's a fair chance the hub's gone. Because they're cup-and-cone once the bearings wear out they start eating the hub, so you end up in the situation where no matter how tight you make the hub there's always play. When you get the hub open, bin the bearings for a start and get some new ones, then inspect the races (what the bearings were sitting on) and the cones (part of the axle that keeps the bearings in places). If there are dents in the cones then they can be replaced, but if it's in the hub you'll need a new wheel as I doubt the rim is worth enough to make it economical to build a new hub onto it.