It is possible to develop depression following a head injury. It does seem as though your ex needs medical help, but he's probably not ill enough for you to do the full works and get him sectioned. I think you probably just have to keep on trying to get him to see your gp and get some kind of referral to a specialist. You could possibly try going to see his doctor yourself and discussing it with him or her.
if your husband is so against going to the dr then can't you request the dr come and see him as a home visit.if you explain his extreme reluctance to attend the surgery he may agree, particularly as he recently had a head injury and his behaviour may very well be related to this.Also has he changed or stopped his medication? or possibly experiencing side effects of his medication for epilepsy, or even the blood levels are a little out... too little or too much antileptics/anticonvulsant can also cause problems..many reasons possible but he should be investigated as his behaviour may well be caused by a physical reason( previous head injury) rather than a psychiatric one.his total refusal to see the dr may well be based on fear rather than being just difficult. it's very difficult for you because you don't really know where you stand,particularly as his moods are so variable.I wish you luck.
Yes, I think there are a number of possibilities. People with epilepsy frequently suffer depression too. Him being like a 'zombie' might have been a mild seizure rather than a psychotic episode. Almost anyone can have a brief psychotic episode BTW, but those who aren't distressed or don’t have a repeat episode never come in contact with medical services. Also it's important not to underestimate the effect anger can have on someone's behaviour whilst going through separation/divorce. It's not really helpful to speculate.
It doesn't sound as though anyone at this time can make your husband go to the doctors and I think pressurising him could well be counter productive. As far as the children are concerned it's their wishes regarding contact that matters. As said above your GP should consider offering you and the children support.