Was the stove cleaned out good before you started it? It may have cloged combustion holes on the burn plate or alot of build up under the burn plate.
Is there an adjustment screw for feed rate on the back of the stoker? I believe turned all the way in (Clockwise) shoudl be max feed rate. It could be out of adjustment, I would set it on max (clockwise in) and wait a while (hour or so) and see how much coal is being pushed, as long as you are not pushing hot coals off the end, you are okay, once that happens, you need to back it about 1/2 turn at a time and WAIT another hour or so for it to settle down, It takes time for these Coal stoves to respond to minor changes in feed rates. Only adjust 1/2 turn at a time and wait to see the results, it may take a few hours to get it adjusted properly, but worth the wait!!
Hang in there, sounds like you are close.