I know exactly how you feel. I had to transition or die, and it has cost me my marriage. Even 10 months in passing isn't an issue and I know that I should I desire it there is no need to be lonely. However, I have kids and they need parents so as much as I wish to, leaving cold and starting again somewhere else isn't an issue. At the moment all we get from living together is stress and pain and i wonder if we will even get to this xmas without a major blowout.
But, I know that if I had not transitioned I would not be alive and yes, the cost to her is high, but death is worse.
Its still the best decision I ever made.