Hello Darknight, it is so nice to meet you. You & your wife obviously have a very loving relationship, that is the most positive thing here. The trust she has for you will be essential to her waking up to the Borg. The others here are right you have a perfectly good reason for stepping aside (not down) so go for it. The time you gain spend with your wife, go for drives to no-where so she can just talk, walk & hold her hand, have a weekly movie night & watch happy films ect. You get the idea, build even more on the trust you already have.
The loss of two, wow, you both sound very brave individuals. Your wife sounds like an amazing woman. The emotional strain for her must be huge, I think the most helpful thing for you both would be to seek out a good Psychologist, you are not required to tell anyone that your doing this, it is personal to you & your wife. You may go together or alone or separately there are no fixed rules. A woman may prove to be the best bet for your wife. Most people can say sorry or give advise which we are all doing here however speaking to a trained professional who will listen as you pour yourself out can really help in the healing process & you can be sure that it will go no further. Go talk to your GP, they usually have good recommendations. BIG HUG for you both. Sabin.