The way he tells his story makes his DPDR and recovery sound legit. But the method here does sound like a scam.
He says he googled many things and found that NAD could help. But I googled "nicotinamide adenine dinucleotide depersonalization" and mostly find his video, so I don't know what he found. The first result I got is a post on this forum in 2018 (posting a link to this very video, which came out in 2017) of someone who tried it and said it worked, but one infusion costs 600£, and the person said it took one month to work, whereas in the video he says it took 3h to feel the first effects, and 3 days for them to increase. The person on the forum claimed to be 95% recovered, but kept posting things about potential future treatments and suplements months after.
Also I think anything that contains the words "holistic", "natural" and "no side effects", should count as a red flag.
Apparently NAD is considered a supplement, so it isn't subjected to the same rigorous testing as medicines before being put on the market, and they don't even have to prove it has any effect before being allowed to sell it.
It is also sold as an anti-aging therapy and other articles say there is zero scientific evidence of such an effect.
So for me it's most likely a scam. But if some people don't mind being scammed and still want to try it, I might change my mind if you all get reproducible results. In the mean time, imagine how happy you could make a homeless person if you give them 600£.