So sorry Neil, you get answered first up by 3 past CALS in a row...
It was the same here really, Chris believed he was fine to drive, hey he was being careful!
The reality is that with either or both legs and arms not receiving nerve impulses correctly to the muscles your reaction time is decreased and in fact impaired. So whilst you may drive the actual car ok, your ability to react and control a sudden situation on the road (probably caused by someone else doing something stupid or unexpected) are just not what they were.
The insurance issue is real - you won't be covered and you and your wife could lose everything. I think it is much more a case of being a real man than a cripple to accept this, even though I do understand it feels like something that is crippling you. Chris had his doctor insist he stop and sign a certificate of medical incompetency and yet he blamed me and made things awful over it for weeks. Please don't make your wife pay for this decision, it's not you, it's not her, it's the effing monster named ALS.
hugs mate, please listen to your wife, we do see clearly.