Troubleshooting Cat Stove - pls help

[Time Zone]

Disappointing performance with fancy feast stove (just the can and holes) this past weekend in 40F weather, minimal wind (about 0-3 mph). Setup is:

- stove insulated from cold ground via wood, and a foil covered foam disc under it.
- allowed bloom time 30-60 sec depending on which "trial"
- with and without Al flashing windscreen. Seemed to be oxygen starved with it (in the AM, but not previous night). Windscreen elevated about 1/4" off surface with binder clips, to allow for airflow. Screen open about 1" on handle side of pot; otherwise was about 1/4" to 1/2" clearance around the pot circumference
- water may have been close to ambient temperature, as it was sitting out overnight as the temp dropped to upper 30s by dawn
- pot used was IMUSA 0.7 qt (660 ml) aluminum mug, approx 3.75" diameter. Fancy feast can is 2.25" diameter
- denatured alcohol used (from Lowes)

the water did warm, but never got to rolling boil or even simmer. I recently started using Al pots to help with heat transfer (vs. stainless) but this cold weather performance was really disappointing. I did notice the handle warming more if I let it hover over the can, instead of resting it on there ... indicating better heat transfer.

I like the pots I have, but they may be relatively narrow for their capacity: 3.25", 3.75", 4.25", for 710ml, 660ml, and 1.4L, respectively. Is it possible I have the wrong kind of alcohol stove for pots of these diameters? For the pots I have, Would a "top burner" or stand help? If the windscreen is always going to be open on one side due to handle, is elevating it for airflow unnecessary?
Only rolling boil I got was previous night when it was probably in the mid 40s. Picture attached showing flames relative to pot. Flames (when they finally showed up) were mostly blue, but the occasional yellow flame appeared.

IMG_3929s.JPG