Just a couple of thoughts on getting even temps with wood. In my experience the key is getting a good bed of coals going, adjusting your air intake until you have your desired temperature, and then keeping your fire going by feeding it sticks at regular intervals. The word "stick" is important as they light faster, don't produce as much of a flash of heat when they are burning with a flame, and turn to coals more quickly than "logs". I consider a stick to be split wood that is about 2/3 the diameter of my wrist, give or take. If you've been using logs instead of sticks that could be part of the source of your temperature swings. I mention all this because I see you're using a log in your gas smoker contraption (and that is genius, as mentioned already) and in the back ground on your wood rack.
There is no doubt that stick burning requires more care and tending than charcoal or lump. It's all a matter of one's disposition as to whether you see it as a needless hassle or a rewarding experience. At times I have the patience for it and at others I most certainly do not.