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