Autumn,
Did you mean to post more details regarding his head injury or is this really all you have?
All I can do is to try and say where I would begin, you may already have tried some or all of it. Are you UK based?
First of all I'd try to establish the extent of injury, time unconscious, time in hospital, length of rehabilition (if any), and area damaged. If it as me I would definately ask questions until I had all the information I had any chance of getting.
Secondly I would look at the 'whole' situation, I would write down the answers to these questions (and probably others that came to mind):
* What is it that concerns me most about his health and why?
* What do I think 'should' be done?
* What dilemas am I left with in living with him?
* Do I feel as though I'm taking the role of carer and why?
* What do I believe would happen without my care?
I would write the answers down, re read them and try to evidence/be objective as much as possible. Once I had some structure in front of me I'd contact a helpline or charity dealing with head injury (they may suggest another line for addiction or may recognise a common after effect - I don't know). I would start with the head injury because it's less subjective and hard as opposed to soft damage - I'd figure I need that info first.
Ok now's where I'm trying to express how I'd make a decision - there's no more to it than how I tend to go about things - it may well be rubbish! I'd try to put into percentage terms the extent I feel things are not as they should be, how much of life is impacted on? What is the extent of the impact? and the last bit a complete guess would be how much I felt was due to head injury. If I felt it had a considerable impact 50% or above (??) then I'd probably look for longer term support for me, a relatives group, internet resources, a drop in center.
In the mean time I'd start my own reading but use helplines to 'touch base' and keep myself on well recognised tracks. I did that reading about alcohol, I'd ask if my understanding sounded sensible until I felt confident.
The only thing I wouldn't do is stick my head in the sand!!! Nothing of the above is about manipulating someone - it's about being aware and knowing where help can be gained. It's hard to do that in an objective way in a crisis.
Here's a start:
http://www.headinjury.com/