Sounds to me, like the "filter bolt" as you called it, may be bent from true. You will never get a good seal then (was the bike in an accident before ?)...
In a pinch, you can peel the old rubber gasket from the old filter and double up...but this is just a temp fix. If the leak stops, then, the shaft for the filter is bent, or the plate where it mounts is bent...
If you know a carpenter, have them check the shaft for square to the plate...from 4 sides...not that hard to do, used to do it to 151 ci Iron Dukes since the filters were low and on the side and vulnerable....theyre's screwed out to replace, dunno if the Vulcan's does...