oops, not -20f-- doh, sorry about that .....

so 20f then is about 7c, just about what it is today here in fact, a pretty warm day for us.
Ya, all the stuff you mention, balaclava etc is all the same stuff I use commuting. I've had to get the balaclava out a few weeks ago as we got closer to freezing. And all the various wind blocking layers for body and legs work, you just have to figure out what works for you--I use the same clothes pretty much for my fall and winter biking as all my other outdoor activities, using varying layers and whatnot depending on the actual temperature, and just keep using the same clothes year after year.

as for feet, I have some older boots that have room to put larger wool socks in and still are not tight-this helps with cold feet.
I also regular use my rain booties just for cold protection, and stick old pieces of fleece on top of my shoes as insulation or even wrapping other old bits of fleece around my ankles before putting the booties on as a wind stopper--but again, for commuting I don't have to worry as much as being out all day---the one advantage with these bits of fleece is that they weight hardly anything, I have the booties anyway, and along with other stuff like fleece neckup , or a thicker balaclava, all these things can make all the difference in one not getting chilled, but take up so little room that its totally worth having them in case needed.
I also have some outer mitt shells that I put over gloves if it getting really cold, cuts the wind and helps so much with hand warmth--again, small and quite light, so totally worth having in my pannier.