Base layers should (ideally) be skin-tight. If your lower-back is wet, your thermals may be too loose there and unable to wick since they're not touching. If your whole back is wet, I would look into the material of the base-layer and the breathability midlayers/jacket. Perhaps you need to remove a mid-layer to increase ventilation. I try to be on the chilly side when standing around. That way when you start moving you're not instantly overheating and sweating.
You may try drinking more water, and consuming more calories while exercising. Dehydration can be a major issue and directly relates to vasoconstriction. When your body decides to start conserving energy it can also start shutting down flow to the hands/feet as it maintains central-core priority. Snack on high-calorie stuff and keep your metabolism high, and drink tons of water (hunger and thirst are both reduced by cold weather.) You have to be proactive.
As a test, depending on your local weather, is to go out for long walk(or better yet, a run) some cold night, or a cold evening hike. Get your blood pumping a bit. Wear your ski clothes, but normal boots. See if you still have foot issues when you're not using ski-boots. Try with varying levels of clothing on, including on the hands. Look for the signs of Reynaud's. If you can go for a run in a pretty-cold environment in minimal clothing (base-layers, thin gloves, beanie, shorts, tennis shoes) while staying well-hydrated and not have issues then your heat-generation is okay and I'd look more closely at the gear. I can play tennis (t-shirt and shorts) for hours in the 40s no problem once warmed up. It was ~42 last Tuesday and I played for 2.5 hours (in the dark) but everyone is different.
If you go out well-hydrated and your run keeps you warm except for your hands/feet then that also gives you someplace to start.
But, personally, I would start with hydration and calories. Those are cheap and easy to work on.