IS the survival blanket the thin disposable type or the more sturdy re-useable casualty blanket. I would try to make an arguement for including the re-useable model, it could fit in the camelbac bladder carry pouch as further insulation/padding for you back? If not- O well !

I would ditch the 12ft. of nylon cord. Replace it with Paracord shoe laces. Even when you pull the inner cords you still have the sheath to tie your shoes. You could also add the countycomm
razor knife and saw to your boots just like you tie in a spare dog tag.
pc of colored cloth for hook lures and/or fish fly, trebles?

Button compass, in the last big war they were small enough to swallow if you got caught.

More water tabs, 8 will not last 3 days in any amount of heat.

Not sure if I would carry a jetscream whistle or not, do you want everyone to know where you are or just signal to those close by? You can get decent small flat whistles at a boat or dive shop.

switch out the ziploc for a turkey oven bag.