Well, it definitely stops spasms, which I believe most stroke victims have.
And I'm sorry that he has to endure that. I was lucky enough that while it did paralyze my left side quite a bit, it didn't really affect my speech much or my cognitive function at all. The small slur was gone in about a month, and after the first 6 mo, I didn't need a wheel chair any more.
I'm not sure if the marijuana helped with that though, but I'm sure it won't hurt. Seems I recall marijuana helps oxygenate the brain. If so, that's helpful for nerve regrowth.
Also, you might have him try lion's mane mushrooms. They also help stimulate nerve growth.