It sounds like you're in an emotionally abusive relationship. You might be and not know it, especially if you have low self-esteem. I mean, however unhappy you being transgender makes her, her acting suicidal as a result suggests serious issues. It is an extremely inappropriate and manipulative response. She may be Borderline or something.

I think you should encourage her to get professional help regardless of everything. I think that, even if you try to be repressed and not transition, your relationship might not last with someone who is that unstable. The longer you go, the heavier the feelings of self-imposed entrapment will be, and just being around someone who isn't comfortable with you dressing or living as you want will become suffocating.

At 27, you're still relatively young and have a lot of years of life ahead of you. At least check out trans timelines to give yourself some sense of what is possible.

As for the work issue, I guess my recommendation would be to do what I'm doing, which is to avoid coming out at work until being fairly passable is possible. In my case, that will mean facial surgery, and I'll probably try to switch jobs as well. There is no reason to jeopardize your employment. You could present female part-time instead.

As for figuring out if your desire to transition is valid, nobody can tell you. You have to make the call. I guess the thing to think about is where you want to be in 5, 10, 15, and 20 years. Also, it would be good if you could find a way to think on this without the influence of your wife and the fear of losing her since that will make it difficult to think rationally and to determine what is best for you. What would you do if you were single?