A few more thoughts:
Double pane windows help a lot. They even have a thermal block so you don't have the metal frame on the outside conducting the cold inside directly. However when they routed out the window opening in the TC, the manufacturer left lots of room so the metal frame cools off the air space and then the inside window flange. If you remove the inside window flange, you can use door/window expanding closed cell foam to insulate these spaces. Less ice on the inside window frame.
You can make the windows warmer still by taping inexpensive, clear shrink wrap film (Walmart and hardware stores) to the inside of the windows to make them triple pane. In another post Photomike made nice acrylic interior storm windows.
The back door in TCs aren't very insulated. Having an insulated curtain/quilt to hang in front of the door at night makes it warmer.
My TC needs around 10,000 BTU/hr to keep it warm once the temperatures drop into the negative range. With an electrical hookup, I have forced air electric heaters for both the basement and the main cabin, and I use an electric blanket to pre-warm the bed.
Consider changing the oil in your generator to a synthetic 0-30W or 5-30W, if you haven't already.
Consider practicing with the cat too, if it isn't used to the TC and cat carrier. Cat treats go a long ways to making it painless.
Consider driving with the furnace on to keep the TC warm. Power supplied by the truck, vs. the TC batteries. It takes a long time for a TC to warm up.
If you winterize, don't forget the outside shower. We run full utilities all winter long for our ski road trips. However, divert valves have been added to the outside shower and city water plumbing to allow these to be drained and blown out to prevent damage due to freezing.
If you start doing this a lot also consider getting AGM batteries, they are sealed and as such you can insulate / heat your battery compartment for much more battery capacity in the cold. Additionally if you deep discharge these batteries they can be recharged from a generator faster and aren't damaged by freezing like a flooded battery would. Flooded battery electrolyte is more water like when deeply discharged and will freeze, destroying plates and connections)
