I think it's beyond thoughtful and caring of you to be here for your brother. You can learn everything in this community so keep asking questions!
You will get a different opinion from everyone when it comes to the topic of supplements, what may help one person has severly harmed another so it's really about gently testing and starting in very small doses if supplements are the route you want to go. My personal advice would be to give him some time and see how he's doing. Histamine issues, food sensitivities, issues with sugar, caffeine and chemicals in general are extremely common when going through WD especially in the early days. So until you know how his body is reacting to the CT I would personally hold off on adding anything supplement wise. When it comes to diet I truly believe that a clean, whole food diet is the best approach. I look at it like "getting out of the way" for your body so that it has the best opportunity to heal. For me, that looked like no caffeine, no processed foods, no sugar (unless natural from fruit) and making sure I was eating plently of plants to promote the best possible gut health (because we know benzo's have a tendency to destroy our guts).
Like [...] bell said, sadly there is nothing that makes us recover faster - if there was, everyone would be doing it! But I do think there's things we can do to help make the symtpoms "easier" while we are in this. Manage stress so you're dealing with as little of it as possible, eat a clean nourishing diet (whatever that looks like for you), make sure you're moving, even if it's just for a small walk around the house if mostly bedbound/severly symptomatic and distract, distract, distract!!!!!
I'm so sorry your brother is going through this, I wouldnt wish it on my worst enemy. Please know we are all here to help in anyway we can.