Adam, the best advice I can give you- read, read and read some more. I also live and hike in the Seattle area, so here is my take on your list-
Backpack: REI Flash 18- Unless you have a sub 5 lb base weight this pack might be on the small side for you. I would suggest the Golite Jam also, it is on sale at Backcounty for $119
Sleeping bag: Big Agnes Pitchpine 40deg SL- I think this bag is not warm enough, I was out last weekend and it was 28* in the desert, I was hiking by Vantage. I've had it snow on me in the cascades in August, 2 years ago. I agree with the WM ultralight but it is very expensive, so you might look for a 20* bag on the gear swap or at Backcounty
Sleeping pad- don't get the BA clearview, you will freeze- I know this from experience. If you can get away with a thin pad go with a Z-rest from Therm-a-rest or get a lightweight Self-inflatable, if you have money left over you can look int the "insulated air" mattresses, but they are very expensive so I'd add them later.
Sea to Summit Thermolite Extreme Mummy Liner- I don't think a liner is worth the price or weight. They don't add more than 1 or 2 degrees of warmth.
Cooking: Backcountry Titanium 700ml pot- this would work, your choice
Esbit folding titanium stove- works
Jetboil plastic spoon- any lightweight spoon work- I'd get a long handled one
Marmot Precip Jacket- good option for a start, you can get something lighter
REI Convertible Pant- personal choice, I don't like hula hoops around my thighs. There are options at Backcountry
REI Revelcloud Vest- unless you don't get cold I'd get a down sweater, Backcountry has a few on sale right now.
Shelter: GoLite Den 2 Shelter- there are lighter option available
Adventure Medical .9 Kit (I think that's the one)- you can make your own for less money and lighter
Petzl TacTikka Headlamp, get the Petzl E02 P2 e+LITE, its better (lighter and better)
long underwear- capilene is good, but I think UL wool is better
hat to wear while sleeping- I like a wool skull cap or 100 fleece balaclava, Amazon had some on sale for $6.95 last week- vary nice for the price.
shoes (I was thinking of getting these at Nordstrom Rack as they tend to have some nicer outdoor shoes on occasion)- go with some trail runners! I don't think the rack has any so you will have to go elsewhere. They have a number at Backcountry
the 10 essentials- search the forums for the best, cheapest and lightest things for "the essentials"
I think you can get a lot of what you need at Backcountry with your gift cert. I wish someone would have given me something like that when I started paring my weight down.
You might look at the "Gear List" forum and use some of those as a baseline for what you might want to look for.