There's quite a bit of weight to be saved if you want to spend. You could easily shave 500g from your pack with a light frameless option. Gossamer gear kumo, atompacks atom etc. A plastic liner is cheap and super light too, saving more weight.
I'm not really sure what the sleeping bag is but a quick Google says it's climasheild. Down is lighter for the warmth provided, down quilts are lighter still.
If you're not expecting midges, then ditch the inner for a polycryo sheet which will weigh less than 50g.
You have a lot of spare/sleep clothes. I usually have leggings or windpants for camp and go commando (at night).
The slippers ARE a luxury. Just wander around barefoot or take bread bags to put your feet into wet shoes at night. I hear you though, the last thing you wanna do after a 30 mile day is put smelly wet shoes on again but unless it's close to freezing, barefoot at camp is actually really nice unless you spend ages standing around on cold rocks or bothy floors and let's your feet breath.
BRS 3000 is the lightest stove afaik, cheap and less than 30g. But if you're only out for one night, do you need hot food? Also, you canister weighs 100g, the fuel is consumable.
Ditch the GPS. My phone has never led me awry, and should really only be a backup to your paper maps anyway.
Swap the petzl for a nitecore nu25 and make a new headband with some shockcord for a 55g saving.
Do you need gloves and wp mitts? Genuine question, some people get cold hands. I take a pair of liner gloves and almost never wear them unless it snows.
Your FAK is heavy, a couple of alcohol wipes, small plasters, steristrips, a couple ibuprofen, a needle and a tick twister is all you really need imo. I put my fak in a coin bag from the bank.
Water filter. Isn't a trailshot a pita to use? Sawyer, platypus quickdraw, katadyn befree are all great options and lighter.
I'm still not really sure what fast packing is. Is it backpacking with some running? Is it just walking a good distance each day? I don't run but frequently do anywhere from 20-40 miles per day. Am I a fast packer or just walking/hiking/backpacking relatively big miles.