be gentle on your adjustments and give the barrel time to react. Make sure you have the barrel and lid sealed. There are a few different schools of thought on the riser. My experience is that the riser has no effect on performance since the rate of air movement is so slow. Other brethren who have built as many or more barrels than me refuse to use them. If you can get a comfort level with the riser I can tell you that you will be happy you have it when its snowing like Hell(thats in Mi. isn't it?) and your barrel is half covered in a drift. I don't think your intake riser is big enough as my winter barrel has a 1 1/2"id pipe- but its the only intake. BTW I have done many overnight cooks where I hadto shovel my way to the barrel and it was perking along at around the 220 with no problems.
I'm curious as to how(and what type) your charcoal is burning and if its burning down one side? I'll have to go back and see what your basket looks like to see if that is a problem.
keep working at it because no doubt you are close to some smokin good food!