1) i don't let the air out of my tires because a) if a sudden warmfront moves in you will have to air up the tires before heading out. and b) my tires stay filled for a very long time. they usually only need a top-off after being idle for several weeks.
2) riding in the cold isn't that bad. you don't want to overdress because getting sweaty can make you colder than staying dry. so the initial start is awfully cold. but ride hard for a few minutes to warm up then take it easy to keep from getting all sweaty.
Clothes: i wear neoprene gloves, north face apex jacket and a nike dri-fit tshirt, thermal tights and jeans. if its raining then thermal tights and rain pants, if its raining and very cold i wear thermal tights and jeans and the rain pants. oh and goretex smartwool socks in any temp under 40. we don't get -18 here but i rode in 10F and it was just fine.