guess i can throw in my.02 worth on this
first off hitting the drum with a hammer would be a LAST resort as it can warp the drum, if you plan on trying to save the drum just in case it is salvagable and can be cut back smooth.
Just be prepared to replace it because in alot of cases you will have to because of the wear creating the lip holding the drum.

The mfg of the drums only allow a certain amount of wear anyway like on car drums and disc rotors and most cases its not much wear before they deem it unsafe to use, so replacement is probably inevitable anyway.

But to get to the part about removing it
several idea have been brought forth here on how to get it off.
I have ran into this before several times and sometimes you can get to the adjuster and back it off completely and the drum will come off once you get the shoes centered.
In other cases i have had to take 2 large prybars and just wrench the drum off breaking the hardware holding the shoes etc.
If the shoes are worn that badly and the drum is worn out that much you will have to replace everything anyway so forcing it off is no big deal.
Just be prepared to buy a new drum and shoes and mounting hardware because i can assure you if its worn that badly i doubt the parts will be reusable.

good luck and be safe... doing this can put you in a situation that may hurt you so just be careful.