Thank you for your insight, it is hard as an ex to get any real medical info. I hope for my sons sake that his father has the same resilience and strength as you.
Three months is still very early days for your ex husband, as time goes on your ex husband will improve alot more. I had a major stroke, and came out of hospital in a wheelchair, with an eyepatch and my hair shaved where I had brain surgery. 22 months later I do not need a wheelchair, I have no eyepatch and my hair has grown. Things change so much with time and they will with your ex husband.
As time goes on your ex husband will be less dependent on visitors, but at the moment he is.
Your son must get on with his own life, and as you say must deal with all this in his own pace. Explain to your ex that it is a long way for you to travel and also that your son has certain activities that he has to do sometimes at the weekends but assure him that your son can phone him and tell him all about what your son has been doing. I hope things work out for you, it's just a shock for everyone involved. But it the situation will get better over time.