Run the flu down closer to the grill to get the smoke lower and closer to the meat.
Try two thermometers low and to the right to get the heat exiting the firebox.
One low and to the left to check the heat opposite end of the barrel.
Might add a short tunnel to have the heat enter the barrel a little more in the center and not all at one end.
Smokers are a commitment, I'm not that patient.
Do you have a grill on the firebox so it can be used as a small bbq too?