My experience in the Wind River Range is limited to the August 20 to September 20 time frame so it may not apply if you are entering much earlier.
I have a WM Highlite Bag and know I would almost certainly be cold during "normal" conditions at the end of August. I have pushed my bag down to the low 30's F with extra clothing but I was not happy about it. The same comment can be applied to an R2.5 pad–it is probably OK for most nights but a little marginal. Maybe add a half length of 1/4 inch CCF pad under your torso? Or use the Circuit's integrated pad? Most likely you will see low temps in the 30's F but 20's are possible.
Having said the above I will now partially contradict myself. Last September during my three night trip the temps never dropped much below 40F and I was toasty using an EE ~27 degree quilt (overstuffed so the number is odd). For a one or two week trip I suspect you would have a few cold nights with your sleeping gear.
Like you, I always carry extra underpants
and never use them. Maybe next year I will be smarter and leave them at home. You will have many sunny days and opportunities to launder clothing.
Again, you might squeak by with an R1 hoody but I would take a light weight down jacket.
What I am seeing, to sum up, is that you should probably plan on temps 5 to 10 degrees colder than your gear list suggests.
Sawyer filters work great in the clear waters of the WR Mtns.
Water crossing sandals are not needed if you can tolerate occasional wet feet. I cannot think of any nasty/scary water crossings after mid August, but I have not covered all the trails, either. The deepest one I can recall is the outlet of Roaring Fork Lake which is above the knees and requires some care.
Depending on which part of the mtns. you travel (Shoshone or Bridger Teton) you may need to observe food storage requirements, i.e., hanging or canister use. If you choose to hang do not use minimalist spectra cord–it WILL get stuck and become unmovable (don't ask me how I know). I now use a flat tightly braided nylon cord successfully with the added benefit that it is easy to untangle.
In addition to the bug head net you might consider carrying some bug repellent. Second hand information from friends indicates that the mosquitoes are bad in early August. I also did not see on your list items such as toothbrush, repair kit, small knife, lightweight gloves.
One optional item, though maybe not needed if you exit the mtns. before September 1, would be rain pants. I debated their use for many years, almost convincing myself that they were unneeded. I changed my mind after discovering how much warmth they added during wet snowfalls.
Have a great time and don't be discouraged by all the cars at the trail head. After a few miles of walking you will find plenty of solitude with a little effort.