Joanne,
You were one of the first persons in here that I identified with because of the age, attempts to keep your marriage intact, slow transition and very high values!
I understand about your wife wanting a divorce, put yourself in her shoes, if I were a cisman and my wife came to me and said that she was a transman and wanted to transition. I know it would not be easy for me to accept, it would take a while or maybe never!
You have mentioned that she has known about your desires for 20 years or so, so it is not betrayal, it could never be betrayal! It is just the natural progression of your inability to handle being in the wrong body. Of course you like to wear a bra, I cant wait to need one! I already occasionaly wear a bra in my house with padding without needing it, it makes me feel feminine and good!
BUT don't destroy yourself drinking, Yes, right now I am also kind of depressed, but drinking or hurting yourself is not the solution, Go Exercise!! You will feel better and will fit on that dream dress you have always wanted, even with your big hand and bold spot ( I am on the same club, that is why I remember so well)
Have patience, ALL bad things will pass one way on another.
Emily