You probably need to pull .6 for the draft with coal. The air must feed from the bottom, no air above the fire, it will kill it. One of the most important things is having a deep enough bed of coal. You cannot build a "small" coal fire, it must be full, you can throttle it to the heat you need.
Check to make sure you have a good air supply, open a window near the unit slightly to see if the draft picks up.
I have a hand fired boiler and learned very quikley to rev the fire up for a few minutes before shaking it down (draft through the ash door). Shaking a cold fire is a sure way to kill it. Get it good and hot, shake it down good and bank it well. Let it rip a little bit with the fresh load, then damp it back down. I think the colder it gets the easier it is to tend as the draft picks up.
Coal has a sharp learning curve, a few cuts later you'll be a pro.