I'm also a bit late. In some ways your wife is 100% correct with the "Slippery Slope" argument. I've been on/off low dose HRT several times over the past several decades. It works. It eases the anxieties, stops the overwhelming racket in your head, you feel better being you. I always had to stop when the point came months later and long after the peace treaty, when things started happening below the belt. A direct contradiction with trying to be a normal(ish) guy.
Six years ago after the excrement hit the air handler again in my life, I knew I needed to seriously do something about how I was NOT handling being trans. Without a doubt, after two failed experiments in my younger days, transition was absolutely the very LAST thing on my to-do list. Nevertheless, I was in the boonies now, needed support of some sort and eventually found a "local" support group some 90 miles away.
I was totally blown away after my first meeting. Actually being in a room filled with others like me, having almost the same stories and feelings as me. "OK a one time fluke" I thought. The next month, the same thing. By the end of the third meeting I knew I was rapidly approaching, if not passed, the point of filling in my wife on what's happening. (We were living several states away due to my new job) When she learned that most to about all the members were either transitioned or working towards it, she was even more concerned. "A duck hanging out with geese is bound to think she's a goose"
A funny thing happened on my way to self actualization, slowly transitioning was no longer absolutely the last thing on my mind. As I slowly learned, actually unlearned, I began to once again see and even experience joy. Joy is addicting. Especially when Shame & Guilt are not always coming around to kill it. Low dose HRT eventually led to higher. The emotional effects of lowered T and higher E were profound. Same for feeling the results of the hard work on healing myself.
Of the many things I learned these six or so years is that how you feel today is not necessarily the same you'll be feeling tomorrow. Like 30 some years ago when I told my wife about my gender issues, failed experiments, HRT, that I was "Just a CD".
She is far from happy about the updated letters. She is very happy about the updated me, as a person. Over the years I turned into a lifeless, soulless thing, always angry says she. Today I live in total fear of ever reverting back to that thing I was. I live in fear of needing to go further then I am. Want and need are different. In a perfect world I would. Mine is FAR from perfect.
One of the other things I learned is it is difficult to be be totally honest with others and even more difficult to be totally honest with yourself, when you have no idea who and what you truly are. I don't know if I'll ever know. I do know a lot more of who the real me is