Get him neutered first of all, and after doing some rehab with him as 14+K suggested, if after a couple of months there is no improvement, I think for everyone's safety and sanity he should be euthanized, as he is a danger. I usually don't recommend this, but there are some cases where it should be done. This may be one of them.
"We humans are indeed fortunate if we happen to be chosen to be owned by a cat." -- Anonymous