Hi Steinke. Sounds like you are having a little of the 'Bituminous Blues'.
A trick that worked for me with the fines: shovel the fines into a paper grocery bag, roll it up so it is about 3-4" in diameter, sort of like a paper wraped log. Place the bags with rows of big coal between them. When the paper burns off, the fines will be in rows, the air will be able to get through the big coal and burn away at the sides of the rows of fines.
Later, like maybe an hour, you can go in a whack the log shaped fines into several pieces, increasing the surface area and the heat output.
Another trick is to put a split of wood between the rolled up fines, does about the same as the big coal I had a shortage of big coal, it sounds like you have it available anytime.
I'd sift the coal, that 's what I ended up doing, Get a pitchfork, with close together tines, it worked for me.. With your big coal, it might not, you may want to borrow a pitchfork first before you cough up the cash for a good one.
I wish I had good bituminous available close by, cheap fuel and my underfeed stoker made for bituminous, I'd set it up and let 'er rip.. But bituminous is only slightly cheaper than Anthracite by the time I factor in the miles and fuel, so I'd rather burn the Anthracite.
If you insulate the chimney with foam, use foam with a layer of reflective aluminum on it, the foam doesn't like heat very much... [don't ask
Sounds like you have a pretty good stove. something to be proud of.