*hug* Whatever you do, please don't make rash decisions at this point. You are poised on the brink of a definite step, to which you have been building. It is natural to balk a little when you see the road ahead.
Ultimately, this is about *you* and your happiness. If after reflection you decide you're not ready for it now, get the letter, keep it, store it in your important documents... there is a very good chance you will be one day. Even years down the line, if your letter isn't accepted because it is out of date, it should save considerable time with a therapist.
And I would suggest you listen to your wife; she obviously loves you and wants you to be happy. She knows (from your post/past posts) that there will be changes. With a low dose, hopefully these changes will be slow enough to allow you to transition together.
Whichever way you know, know that we support you and will do our best to help you in your transition, whether it be delayed or not. You're still family... I'd venture to guess we've all been in similar situations.
*hug*
Oh, and feel free to PM me if you'd like!