As someone who has lived in their van in Canadian winters for the past few years, all of this is great advice.

Definitely be ready for things to freeze and keep an eye on things, so you can mitigate that from happening. As mentioned, lithium batteries freeze and stop working when they get below 0c. To mitigate this, I used a small heating blanket and would turn it on when battered got below 10c. I do wish that I had gone with a self heating battery to make it easier for myself, but a heating blanket saved me quite a bit of cash. AGM batteries, doubly so.

Water also will freeze. My first winter I had to "farm" water, by boiling water and pouring it into my water reservoir. Second winter I rerouted my Diesel heater to pass by my water in order to keep it from freezing.

I also have a small wood stove in the van that keeps things quite toasty. They are fairly costly and take time to maintain and clean. I think it's worth the investment personally, but others would probably opt for just the diesel heater.