I removed the drum from the other side without removing the cotter pin and nut.
The drum just slides off of the hub assembly. Drum has 5 holes for the studs and one hole in the middle for the hub.
Then that one has been replaced before. If the the drum you are fighting is still swedged on the hub, it will not come off without removing the spindle nut. It sounds like that's the issue. Look closely at where the studs come through the drum. If it looks like some of the stud material is pushed down around the holes in the drum, that's the issue.
