That's a lot of work and money to put into a 160k miles winter beater, you're probably better off just throwing snow tires on it and fixing up the front bumper, then calling it good. I won't drive a focus in the winter without a good set of snow tires personally.
The SVT brake upgrade really isn't necessary unless you are tracking the car and have some pretty serious go mods. Drums are fine for street driving unless you are concerned about looks.
Skip the ebay header and CAI. Best header for this car is a used SVT header and flex. The stock SVT snorkel and intake box with a K&N drop-in actually outperform a CAI. I'd pull the header and the intake box and snorkel from the junkyard where you got the brakes.
And why drop a winter car?
I dunno... the mods you listed aren't going to make a whole lot of difference for the car except for the suspension.