Hi Mirriel,
You sound a lot like me. I've been married almost 21 years and started transitioning a bit over 2 years ago at the age of 43. Coming out to myself was hard, coming out to my wife was harder, but I did both on the same day. You are awesome for not doing things behind her back. I never did anything in secret, and never even presented myself as female in private until I was 43.
I didn't want to be trans one bit, and fear of the unknown got the best of me. I tried to literally drink myself to death twice inside of a month, and woke up in the hospital both times. The doctor who stitched up my head the second time was actually very familiar with transgender patients and begged me to get a proper gender therapist before it was too late. At this point my wife agreed, as she was very afraid that the next time I would not survive.
Please work out what to do in order to manage your dysphoria with a therapist ASAP. I don't know why your wife would be dead set against you trying to find happiness and peace nor why she thinks she gets to dictate that you never will. BTW, my wife loves the "new me". Gone is the miserable, depressed drunk, this is the real me. I'm happy, charming, silly and fun to be around. I fart rainbows and pixie dust and have a positive attitude for the first time. And yes, you can transition in middle age. I will be 46 on Saturday, and I seem to be presumed cis female everywhere I go now. It took a lot of work, but i did it. Finally.
Believe in yourself. Take baby steps and give your wife the space she needs. The T-bomb takes time to process.
Hugs,
Jill