@Sundodger, why are you done with the catcan? I've used a trangia spirit burner last year and while it's a bit heavier it does have the simmer lid and can also snuff it out and then seal it up with residual fuel inside. if you can dial in the fuel required for a cook then there are myriad uberlite alcohol fuel stoves out there. like .5-1oz. These seem very efficient and simple solution for extreme cold. absolutely need a good wind screen.
I went down that rabbithole a bit a year ago and built a couple DIY aluminum can rigs that were OK but there's also a lot of products out there too. PaleohikerMD on youtube is a major nerdout on alcohol stove testing. Goshawk brand comes to mind for commercial products. As long as you have real good windscreen alcohol stoves should work just fine below 0* weather. I don't have 0* weather to test with. Is there advantages to go with white gas vs the super simple and readily available alcohol fuel? higher energy density perhaps?