Hello Laurie, you will have problems keeping the fire going without the combustion fan running.. I'm saying this based on your description of your chimney.. Coal won't sit and 'smolder' like a wood fire,, if there isn't some air being pulled or pushed through the coalbed, the fire will go out. You may want to add several lengths of chimney pipe to the existing chimney stack to raise the height as much as possible.. A good chimney is the heart of a hand feed stove.. A stoker stove can get by with a marginal chimney.
Like suggested above, load the firebox as deep as you can, mound it up and slope it up towards the back.. Coal likes to have a deep fire. It will burn in proportion to the air supplied to the fire, it won't burn all at once.. Just load it on.
Take care,, Greg L