Reddit reviews Rothco G.I. Black Extreme Cold Weather Polypropylene Underwear Top (Medium)

yeah, thermals. something like these.

i will note that once i bought a pair of winter-sports underwear. the ones that "wick away moisture" so you don't sweat. yeah, those actually make me feel colder than wearing nothing somehow.

as for boots, just something with tread that look warm. they could just be ankle boots- you don't need snowshoes. last year i stupidly wore my docs and they have no insulation and slip like mad on ice.

the pea coat will be fine, with an undershirt, sweater, and hoodie under it.