Two years ago I had started the abx about three months previously. When I started my right arm was a useless lump held against my waist. I couldn't do anything with it, which being right handed made things very difficult. I couldn't even do up buttons without struggling for ages with just one hand. Things weren't much better three months on. Now, though, I have improved so much that I noticed only yesterday that I was now using my right hand in preference to my left for beating up omelettes and that sort of thing. Also hitting my husband hard on the head when I saw a mosquito about to bite him!
If he is declining that rapidly from the MS, like LifeontheIce and me, he should manage to make tremendous recoveries. This time two years ago, though, I was crying in frustration because I couldn't tie my boot laces or do up the buttons on my nubuck jacket at all: they were far too unforgiving. Someone said "Be easy on yourself, buy outer clothes and shoes that use Velcro fastenings." Great, I wanted to wear my nubuck jacket and lace up ankle boots, not miles of velcro. The next year I could.
Nothing is ever guaranteed in life, so all I can really say is stick with it for at least six months, probably a year, before giving it up. You were saying that he wanted to stop and go onto rebif, but this certainly won't stop progression. There is no reason why he shouldn't do both, though, for that extra little bit of immunomodulation. He might also care to try LDN and/or statins, but as an addition not an alternative. Several people do this also. So do try to get him to stick with it: you have nothing to loose and much to gain. If he is depressed, melatonin might well help to give him a good night's sleep, without being addictive. This can work wonders.