I'm glad to hear your son is doing so well. I'm sure you're just glad he's doing better- who cares whether it is the cessation of Rebif or the addition of LDN, really.
Having said that, it would have been most interesting to have him (or anyone switching) on nothing for a while before starting LDN, as side effects from the other drugs can definitely impair quality of life. The scientist in me wants to know!
I just mention this because I, myself, was mistaken in attributing some improvement to LDN. I took it for several months, saw no real improvement, and discontinued it. Two days later I developed bladder problems. I started the LDN back up and they went away.
I was about to become a "believer" when I mentioned it to my doctor. He questioned me and quickly traced the bladder problems to, believe it or not, taking too many tablets of Immodium AD. (I didn't know it could do that!). I experimented by taking a bunch at once to see if it would repeat the same effect, and it did.
Turns out it wasn't the LDN at all! Even a jaded cynic like me was almost converted into a believer by happenstance!
Let me be clear, the #1 point, above all, is that your son is doing better, and that's great. But since we don't have good trials on LDN, I hope you'll remain open to mainstream treatments- in particular, I am thinking of Antegren, which may be available pretty soon.
And, come to think of it, I at least can't think of any reason why LDN and Antegren couldn't be taken at the same time. I'm not a doctor, though.
Anyway, bottom line, I'm glad to hear your son is doing well.