Your four items are pretty important. For the sleeping bag, my rule of thumb is to have a down sleeping bag that is rated 10 degrees F better than what I think I will need. Then for a foam pad, I bring twice the thickness that I would use in summer.
Booties are OK, and if I expect to be standing around in camp much, then booties are more important. If we are moving every day, then there isn't that much standing around in camp, so I often skip the booties. However, the ski boots need to be warm enough to be tolerable in the morning. So, when camp is set up, and the sleeping bag is pulled out of its stuff sack, I turn the sack inside-out and then use that to store the ski boots inside my sleeping bag where it will be warm. Then in the morning, the boots come out, the sack is turned back outside-out, and the sleeping bag is stowed.
Lots of hot drinks are important. However, you don't want to be drinking hot drinks into the evening or else you will have to get up too many times during the night. Instead, drink the hot drinks soon after making camp and then again at breakfast time.
If I am sleeping inside a tent, then I dig a hole in the snow right outside the door. That way, I can sit in the doorway with my feet hanging down like a proper seat. The stove is used down in that hole.
If you really want to stay warm, then pack three people into a two person tent. Or, dig a snow cave. That assumes that you have a proper snow shovel.
The most important rule is this. If you can stay absolutely dry, it is easy to stay warm. As soon as you get wet and you can't dry out, that is the beginning of the end of staying comfortable.