I have the same smoker, had it about 3 or 4 weeks now. Are you using a charcoal basket? Oh ya just saw you are.I built one and it really helps. I made it 12" x 12" x 6". I put maybe 2 full chimneys of unlit charcoal in it, I then light about 3/4 of a chimney full of charcoal and put it on top as close to the smoking chamber as possible. I can get it up to 300, I get 4 or 5 hours of burn time this way at 250 degrees. If I use sticks I use 3/4 chimney of lit charcoal and get a good bed of hot coals then put on about 2 or 3 sticks of wood. I can get it up to 350, 400 easy, at 250 degrees I add 1 piece of wood, maybe 3" around by 6" long maybe every hour or so.
I have both dampeners wide open tell I get to the temp I want then start shutting down the intake dampener on the fire box tell it burns steady. I have it open maybe 1/8 of an inch by the time I'm done farting around with it and she burns great. I leave the chimney one wide open.
Does your fire go out or is it just not burning hot enough?
I did about 6 trail burns before I smoked anything on mine, just to try n get the feel for it and see what worked the best for me. In fact, today was my first smoke on it and it went great. Did 2 chickens, didn't have any logs left so just used the little fist size pieces of wood and some kingsford I had laying around and I only had to add wood for smoke twice, 3 pieces each time in 3 and a half hours, heck it held at 230 for an hour and a half after I was done with the birds.
Sorry such a long reply but hopes it helps.