do you just want to remove the part labelled #8? it should be pressed in against the rubber parts #4. It may be in there a bit tight, and with years of gunk and grime holding it in there. I recommend that you hose some WD-40 into the gap around the circumference of the #8 part (sprocket flange) and bolt your sprocket back on finger tight...lay the hub sprocket side down, if you can get the edge of each boot onto the sprocket, you can get a good fingerhold on each side of the hub and pull up, don't worry about pulling straight upward, it's just the sprocket carrier jammed into the cush rubbers, so wiggle if you have to.
Conversely, when reassembling a cush drive, always hose everything down with WD-40 and slip it together. WD won't hurt rubber parts, they rather enjoy the effects.
Those four punched in spots are to hold in a threaded bearing retainer, #3 in the diagram, I think. To remove the threaded bearing retainer, you must lightly drill out the punched dimple areas to allow the part to unscrew. once the bearing is replaced and the cap is threaded back on, you'd need to hit those spots again with a punch to keep the retainer in place. The process is referred to as "staking" a search for that term will find more info.