wonder why I allow my life to be so dominated by my wife's illness.

Well, two reasons are:
legal responsibility

having seen so many cases over the years where mothers (and fathers) are prosecuted for negligence towards children, doctors/nurses towards patients, etc etc, I do wonder what would happen if my wife died from one of her 'seizures' whether I would be prosecuted. If my wife committed suicide could the police interpret circumstances as me 'assisting her'?
There are so many concerns in this respect.

the second is moral responsibility:

If anything did go wrong how would I feel? I would carry the guilt with me till I died. It is an awesome responsibility - one I actually hate - but it is my lot and I do my best :)