Petunia, you are where so many of us have been! Unfortunately, there just isn't a plan or method which will guarantee success as so much relies on the people and situations involved.Your wife seems to genuinely love you, that is, the person she believed you were when she married you. Her concept of you then, and now, has been challenged. Her concept of herself is being challenged.
Time can be your friend. when you marry, you become a couple, and what affects one of you will affect both of you. You have been trying to figure this out for years, and while you may never completely sort it out, you will find a place where you can be relatively comfortable. She needs the time and support to find that place too.
Even if you do transition, you will still be the same person inside.Your values, empathy, outlooks, and love for her will remain. She should know that. Right know, she thinks you might become a different person, someone she doesn't know. She is also confused as to what your possible relationship might look like? If you transitioned, would she be gay? Would people see her as gay? She may not be homophobic, but we of all people should recognise the discomfort of being incorrectly seen by everybody as something you are not.
She is possibly worried that she might lose family and friends, social status, confidence. She had dreams of retirement with a husband and loved ones, holidays and doing things with friends, but what about those dreams now? These things can all be worked on, and understanding can bring a level of comfort, but it takes time.
I made sure my wife understood that I was trans before we married, and she, after a few months, agreed that I needed time to be myself as she could see the distress dysphoria was causing me. (sometimes dysphoria is not disruptive, but is still there and building, and the level of euphoria experienced is an indicator of the relief felt.) We started with some 'me' time when she wasn't home, but she kept arriving home early and 'catching' me, so that evolved to being 'me' all the time I was home, but with the clear message that if anybody saw me, she would leave!
I had promised that I would never transition, and I was determined to keep that promise! Decades passed and I felt I could maintain this forever, but my dysphoria was building. I really fought against my incongruence, and it took its toll on my health. My wife saw my struggles, and when I was sick from it, she agreed I should transition.
She really tried to support me, she moved into a different bedroom, but it didn't make much difference. I asked he what was upsetting her most, and she said it was watching the man she fell in love with 'dying' a little every day, and there was nothing she could do to save me. She was on a roller coaster, some days she would feel confident we could continue, and grow old together. Other days she just couldn't cope. She drove me to the hospital for bottom surgery, brought me home after it and cared for me for 4 weeks post op. I thought we had cleared the final hurdle, but she left.
4 years later we are BFF's, rely on each other for all the things we relied on each other when we were married. She has commented that I am still the same person, but in some ways, a ghost of her former husband. She still cycles through periods of acceptance and grief. Putting her through this was the hardest part of my transition, but I know I did absolutely everything possible to avoid it, and that it was inevitable.
I have no idea how this will work for you Petunia, but give it your best shot, care for her as much as possible, and think about how you will both feel in years to come. Some relationships will survive this, most don't, and so much is out of your control.
Best wishes,
Allie