I had the same issue you're having with the fork lock with my 500, it took me so long to figure it out that for the first two months I had the bike, I didn't even try it was so frustrating.
First a healthy coating of wd40, then put the key in the fork lock, turn it counter clockwise until it stops, somewhere around 1 or 2 o'clock, then, while still pushing the key in, rotate the handlebars to the right slowly, once you feel the lock go in deeper (about a half inch) turn the key clockwise while still pushing in. Once the key stops at 3 o'clock, pull it out. Repeat for unlock, and you may need to straighten out the handlebars more than you think for this to work. That was my problem at least. Hope this helps!
Few problems on this green earth cannot be solved by the proper application of high explosives
'96 Vulcan 500LTD
'08 Vulcan 500LTD (wife's)