Lots of good ideas!
Smoking in cold weather can be a challenge
I preheat my Masterbuilt to 100° and then watch the temp. When it gets below 60°, I turn the smoker on to bring the heat up
An easy way to add some heat, is to place a 100 watt light bulb in your smoker.
You could use a hotplate, but this may generate too much heat for your WSM
Burning charcoal may work, but would be tough to control the temp for salmon and cheese.
I also use a moving blanket for extra insulation on my Pellet Grill
With temps in the teens, it's tough to smoke. We're supposed to get a little warmer weather, and this may be your opportunity to smoke your cheese and fish.
Try a 100 watt bulb, and wrap your WSM in a blanket
Keep us posted!