Actually, sleep is hard to come by during withdraw. He's probably past the the acute portion.
However, depending how much and how long, his body is prolly pretty badly mangled. Most likely malnourished and a severe vitamin deficiency especially, the B complex vitamins. If his liver is damaged, his body can't produce enough glucose, or metabolize vitamins.
I have 6 months, and I'm still healing physically. If I can, I take a short (1 hr) nap daily. I alternate between sleepiness and sleeplessness.
I guess I'm trying to say it can take a while, and booze really messes up your body.