If that brake drum is not coming off, you may have a serious 'lip' on the braking surface inside the drum. This will actually prevent you from pulling the drum off also. If there is no evidence of the lock washers as described by Jerry above, then you may have to slacken the parking brake cable right off.
If that doesn't work, and the lock washers are present, you might have to carefully drill the two studs out with the lock washers. I say two, as I have only ever seen two in place before....I might be wrong here, but I am sure not all studs have a locking washer.
The studs will press out of the axle once it is removed from the housing, so don't fret too much about damaging the studs any further....they need replacing anyway.