This is a nice list. I would make the following remarks:
A trash bag as rain skirt may work okay in parts, but in exceptionally brush areas the bag will get destroyed rather quickly. There are silnylon rain skirts (I think ULA makes one) and just plain old rain pants that are nice to have when the weather turns cold and wet. I was among the last to finish the trail, and I can attest that it was cold and rainy in Oregon and very cold in central/northern Washington come October. Washington is a tricky subject - from living here I know that August is generally the nicest month, but September can be a real crap shoot.
My hands get cold so I brought mittens/gloves with me the whole way. I used them in the Sierra and Oregon/Washington. It can snow in the mountains just about anywhere (look at the pct-l list serve for past five years - people have been snowed off several peaks in SoCal and last year, it snowed in the Sierra around the second week of June. Every year is different, but honestly, I believe the weight penalty to be worth the comfort. But to each his or her own.) They do wet out sometimes - I brought a couple of pairs through Washington but I was weird this way.
I didn't use a fleece. I did bump up my thermals to 200 weight IceBreaker in Oregon/Washington, which was nice and toasty. The Feathered Friends down jacket would be nice to have beginning around Sisters, Oregon. You can send it to Big Lake Youth Camp along with more cold-weather gear. Again, if you are fast on the trail, you may not need any cold weather gear. That much said, the further north you travel, the fewer and fewer the town stops with legit post offices. But you get in better shape so to me, I added gear and the weight penalty didn't slow me down a bit. I had lost way more weight off my body than ever could be gained in my pack by a few items.
Finally, and this is just again, my opinion, if you plan or must night-hike, make sure your lamp is up to the task. I tried with lesser (UL) headlamps and regretted it. You want the very best headlamp with the brightest beam that is reasonable to carry when night-hiking.
You may never need to night-hike, nor want to, but what may happen is that you will need to get to some posto ffice somewhere to pick up your food box/bounce box. You may need need to get there before it closes for the weekend. And thus, you will need to hike into the night. And when your headlamp is lousy, there will be much cursing and slowness. Not fun.
Finally, if you have Yogi's book, great. But she sells these cards with all the town stops including post office/fuel information/phone numbers and even some lodging. Four-card set. Nice to have.
The most important thing is to have fun and not to worry. If you get desperate enough, drop me a line and I can send you something if you need it.