Something is a-miss

Possibly blown head gasket. Pull the plugs and read them. Oil leak on outside plus oil fouling on a plug = blown head gasket. The other possibility, worse yet, is that the head cracked during the cold temps. (How low did it go where the car is kept and what is the AF protection like?)

The soot in the tailpipe could be an over rich fuel mix, like from a stuck choke. It could also be oil mixed in through a head gasket failure or crack. This is why I recommend reading the plugs.