Acknowledging your gender is very much the first step. You must be true to yourself or you will never find happiness. Your wife's refusal to accept who you are is rather selfish, don't you think? You have a medical condition, for which you are seeking treatment, and she is not okay with that? Doesn't she want you to be happy?
I guess that she is more concerned about herself than you. She is worried that you will change as a person. You won't. You will still be the same person, just with some changes in physical appearance. Is she only attracted to your appearance, or does she love the person inside? She may be worried that if people see you as a couple, people will think she is a lesbian. Again, thinking about herself. In a 50/50 marriage, I believe some of those vows were to love each other no matter what. The whole "in sickness and in health til death do you part". Maybe people don't say those things anymore.
My suggestion would be to ask her to join you in a visit to the therapist. Not for her to get counseling, but so that she can ask questions that she needs answers to. Questions that you might not be able to answer.
You also need to give her a chance to adjust. Let her see that you are still the same person. It takes time to adjust to major life changes, and it is true that when she met you, she had no idea that this was on the menu. Help her understand. Give her time to adjust. If she can't then that only means that she is not willing to.
We have many members here who began their transition after they had been married for a while. Some made it work because they truly love each other. When the relationship is based on other things (physical attraction, money, property, children, etc.) the strain can become too much.
It is important to understand that YOU DID NOTHING WRONG. You were born this way. Gender dysphoria does not go away and often gets worse as we get older. How we handle it is unique to each of us. You can do this. Just hang in there.
Hugs!