I grew up on the Eastside so I know what your talking about. I think your list is great. Before you mentioned the bridge crossings I was wondering how you would address that, my plan called for borrowing a kayak to cross the lake if the bridges collapsed and I was stuck there. Also the 99 is elevated at some points (i think) so your distances may get longer on detours. Procuring a bike would make things easier for you physically.
You may consider a 'survival candle' to birthday candles, more heat if you can't start a small fire.
Lastly, consider rain pants like Sierra Design for about $30. Even though you have the long johns, those ex-offico's (wore them for years)are not that great for continuously cold weather. The rain pants will help with body heat when not on the move and weather proofing when on the move.
YMMV
A bike would definitely help in getting home quicker (assuming things aren't so bad I have to carry it half the time). I just have not been able to find a reasonable place to store one at or around work. Probably need research that more.
What kind of survival candle did you have in mind? I actually had a 9hr candle in my pack, but decided to replace it with the esbit stove. Do they make small survival candles?
The rain pants are a great idea. I'll check out the Sierra's. I where those same ex-officio's to work everyday. They are water resistant, but only marginally. Given that getting cold if I have to hike in the rain is a major worry, the rain pants are an excellent suggestion.