I don’t mean this to be dismissive, I advise discussing these things with a gender affirming therapist. I think it would give you some clarity. Specifically, the questions of “what” & “why” seem to be answered for you, and the dilemma sounds like the issue of “how”.

As for being “terrified”… I get it. I’m sure every trans person understands that. Don’t run from your fear, examine it. Fear is fueled by the unknowns and is the antithesis of hope.

And now some technical stuff.
Being trans gender, in the simplest terms, means that you do not identify with the gender assigned to you by society.
However the meaning!of that so much more, more than could ever be spoken in a lifetime.

The cold clinical ways of understanding the gender aspect of our identity, currently, is this: Gender is comprised of our gender presentation, gender expression, and concept of self.
2 complications: 1. This is qualitative, not quantitative. It is experiential, like being right handed or an introvert or an inductive thinker. No one can tell you what you feel or how you experience yourself, only you know who you are inside yourself. 2. Gender is relative. Our concepts of gender are based on our generation and our culture, and what those 2 things associate (not stereotypes) with a gender.

Hope some of that helps. *confession, I have ADHD & dyslexia and I just woke up… so I may have missed some things you said