The flip side of all this - the bike will ride just fine with the cocked wheel. May be a touch of work to correct when riding no-hands but I'll bet it takes so little that you will quickly adopt and never think about it again - unless your brain's gotta know that wheel MUST be straight. Yes, the brake will be a little askew to work properly but that's easy on most bikes and brakes. You've got fender eyes and presumably room for them so you can disguise the skew and not have to look at it.

Second thought - how much vertical play do you have in the dropouts? If enough, I'd try epoxying a thin steel sheet along the top face of the lower dropout. Easy, non-destructive, cheap and not too hard to remove if it doesn't work. I'd use an epoxy like Marine Tex or JB Weld and "cook" it with a heat lamp or 100 watt incandescent bulb with tinfoil around the dropout and bulb.