I know you're not asking, and may not even be open to suggestions -- but at the risk of seeming intrusive or arrogant I'm going to offer a few things I've learned over the decades I've been barbecuing. Even if you don't, maybe some other folks can benefit:
There are three "basic" mods. Two of them are important. The other is incidental. All of them are very inexpensive and easy to do.
The first of the important ones is installing a "manifold" on the cook-chamber side of the firebox opening to force the hot air and smoke laterally. The second is installing an extension on the flue, dropping the opening inside the cook-chamber to cooking rack height. This keeps hot air and smoke in the chamber longer, giving more even side to side temperatures, saving fuel, and improving consistency.
The unimportant mod, fwiw, is moving the thermometer hole to a better place. However, fixed-place analog thermometers aren't very important anymore in modern barbecuing. Digital probe types have superceded them -- especially with remote read outs. More later.
A charcoal basket will let you run higher temperatures and save considerable fuel. At the same time, if you like. Your fuel saving is in the neighborhood of 1/3. Time between re-fueling is increased in the same proportion. Once they've tried a basket, most small offset users wonder how they ever lived without it.
Here's a link to the most popular description of the basic mods (the author, "Bid Dan," also describes his charcoal basket): http://www.homebbq.com/library/SmokerModifications.pdf
Times have changed since the piece was written so Dan's prices are on the optimistic side. I guarantee the two important mods and a basket will improve and enrich your barbecue -- no matter how good it is now.
Tuning the pit, which in most small offsets, means using a drip pan and experimenting with placing a water pan keeps temperatures even from side to side. If you're interested in knowing more about what a water pan does and how it can help you, let me know. The ways it works and helps is a microcosm of the physics of barbecuing. More than anything else, a tuned pit means less turning and moving the food, which means the door is open less. As I'm sure you already know, opening the cook-chamber door more often than necessary is about the worst thing you can do.
A modern thermometer gets rid of a lot of checking and fudging, and generally makes the whole thing easier and more fun. I like the Maverick ("Redi-Chek") ET-73. It's a wireless readout with two probes. The suggested use is one probe for the meat and the other for the chamber, but you can use both for either if you like. Considering the quality of life improvement -- not having to run to the smoker every twenty minutes to check the temp -- the price is very reasonable. There are a few other options just as good or better, but they're vastly more expensive. There are a great number of other units at a similar price which simply don't do the same job. Avoid the Oregon Scientific and the Weber like the plague. The Maverick ET-71 doesn't do the same thing. I like the Nu 701 as much or maybe better for some people, but it's too expensive. The ET-73 is simply the best choice. They're available at a discount ($40) all over the web, here's one site:Redi-Chek ET-73 Maverick Wireless Remote Smoker Thermometer
From your posts, I gather this would be considered a substantial equipment investment. I'd say "worth it," but that's (of course) up to you. Like the basket this is one of those, "How did I ever live without it?" things
People in your climate situation sometimes make insulation blankets so they can keep barbecuing when the weather gets fierce. I've lived in coastal California (nearly) all of my adult life and don't have much experience with smoking in cold weather -- but I'm told a layer or two of water heater insulation faced with a space blanket on both sides, wrapped around the cooker, and secured with bungee cord, makes enough difference to take you into the teens.
If your actual grate temperature is below 210, you're cooking at too low a temperature. Very "low and slow" is the 215 - 225 range for pork and beef. For one thing, you're on the ragged edge of food safety -- in fact, well below what's recommended for pork. People often feel insulted when food handling protocols are brought up. Don't take this wrong, you're not being accused of anything. It's one of those things you can get away with for years without any problems or even have issues and not realize the cause. And, yes, the gummint is way too conservative. And yes, food can be safely cooked at that temperature, but it requires stricter handling at either end. Still...
Safety aside, you can get better results around 225 for ribs, in the 225 - 250 range for butt, and the 250 - 275 range for brisket. These temperatures are not only right for the meat, they're right for the "bark." You will like it cooked more hot. Try it, like it, like a lot. You will like it Sam I Am.
For another, it goes much faster; and since you're cooking in the 190s for food that finishes in the 190s, for instance pulled pork and tender brisket, it must take you forever. Finally, at the higher temperatures you drastically reduce or eliminate the "stall," which makes the whole thing more predictable. Which means you know what to tell your guests, and how much beer to stock for the old man. More speed, more control, more better.
My experience is that injections work best with large pieces or pork and some beef. Like you, I'm not partial to brining large pieces of pork. You may or may not like brining ribs. It's sort of a mini-trend here in the west and you see it with some of the mid-level teams in the CBBQA (a KCBS affiliate). I sometimes do and sometimes don't depending more on whim than anything else -- though I suppose leaner ribs are better candidates than fatter. Brining poulty is pretty much a habit. I prefer it to injecting, even with turkey. Love to talk brines with you. Happy to talk injecting too.
Hoping to hear and learn from you,