Either hitch on a fuel tanker or truck on its way back to Kyrgyzstan, or hire your own vehicle from Khorog.
Same as getting in.
Rice, eggs, snacks, yak butter, bread, mutton.
Tea, surprisingly good coffee, and vodka. Yak milk.
A zealous policeman in Murgab may want to register you with the police or complain if you were taking photos. This isn't a problem, registration should be known well enough simply getting to the area.
There is some risk of altitude sickness.
Same as getting in, either back to Khorog or onto Kyrgyzstan. There is currently no border open with China.