Honestly, I always get wound up any time someone says someone must be a 100% certain of anything. To the extent that I am certain it is what my brain registers rather than what my body is.
I too have similar fears about others, will I be able to pass, what will I look like after HRT, how much will it cost if I have to have FFS, will I have bricks thrown at my windows by some crazy person, etc. If I want, I could focus on all these things, but in the end they won't stop me from having the rather dysphoric thoughts that I do get. I know that I feel better when I allow myself to be the person that I am.
Slowly, I have been focusing on being who I am and building a positive, forward looking life. That being said, I also think about all those risks too, but I put them in their place based on just how important they are to me and the degree to which they too would take away something so intrisic to myself that I couldn't be happy either transitioning or not transitioning (then I compare the results). I also try my best to create a plan to deal for each of these lingering doubts and fears. Although I have my doubts and fears, they really pale in comparison for me compared to finally being me.
I can appreciate how overwhelming all these thoughts can be. They still bother me at times, I hope that you can find the answers you are looking for. In the meantime, I wish you much peace and send a few hugs your way.