I have a similar story and just before I saw your post I was thinking about posting something like 'how long will it take me to get over this'. My son had chicken pox about 6 weeks ago, then very shortly afterwards developed encephalitis. he was v ill and intubated in a coma in hospital. I guess that it's the same kind of thing that your DS had but maybe yours was more restricted to a particular part of the brain. My DS has recovered very well physically but has emotional / behavioural difficulties now, I think. We are waiting for a psych assessment but I think he may have ADHD now. He had a kind of hyperactive (what my DM calls boisterous!) type of personality before, and this has got exaggerated now. I think at the time I protected myself by only focusing on what was in front of me (as I knew how dangerous it could be) but now it's over and he is doing really well, I am kind of obsessing over it a bit, ie what caused it etc, what could we have done differently. We did get him to hosp v quickly though, so I think it's just the luck of the draw.
I don't know about vaccines, I think if I have another child I woudl get it vaccinated, but my BIL, who is a GP, hasn't vaccinated his DS, I'm not sure what his rationale is, but think it's something to do with being better protected later in life if you have the actual disease rather than the vaccination. I'm not sure though, I've been meaning to ask him.
In the US they vaccinate though, don't know where else, I think we don't here simply for cost.
Sorry you're going through this, glad to hear your DS is doing ok. Most people think chicken pox is so mild and my DH says that DS is fine now so I should move on, it's hard though isn't it. I was thinking I will get some counselling if it's still bothering me in a while. Maybe that's something u should think about?