For Sale: Fixed /Track Deep Section Wheels

Thats a good fix mate...The spacer would bring the sprocket out...On the track you shouldnt really use a lockring as its safer if you crash etc...Yep you can always use both sides of the hub for a fixed sprocket....
Heres a tip for ya..If you use the free side for a fixed sprocket you can use an old style BB lockring to lock it down.

Use a lockring on the road chaps..

hmm... if it's just those innermost threads that are damaged, you could try using a spacer to space the cog out, so that the lockring doesn't need those damaged threads? Probably worth checking this out with someone more qualified than me though.

and you run a front brake on the street anyway though right?

I think ideally though, a new hub.