I will always suggest talking to a therapist and will try to offer any suggestions that I can. First I just want to say I am now following my own path. Not my families. Not my "friends". Not their gods. My own path and my own story. Second I am a bit crazy and on a real manic spree so take it all with a grain of salt.

1. I probably absolutely can't help you with your god stuff. I am often pretty anti christian. Like I range from pagan to slumbering old gods cultist. I am even ordained to marry as a priestess to Cthulhu. Like I said. Crazy. And probably no help for your crisis of faith. I just could never understand the fear of being kicked out of a church and the threat that they might do something like that would just piss me off. Try not to let others define you. It is you life. Live it how you want to the best of your ability.
2. Early on I was kind of like you with family. Their opinions meant everything and I begged for their approval. I tried so hard for my mom to understand. Gods I can't tell you how much I it hurt when my mom said I was killing her "son". She said it once and I just couldn't take it. I did some extravagant SH right in front of her and didn't die because steak knifes aren't that sharp because if she wanted to really lose her kid I'd be happy to take my leave. After a cry and wandering around at night for an hour or three I realized I was done with them. I will love them but they will not control me. Fear has a way of turning to poison and those years of repression has grown a hate for them and what they stole from me. Or well, I stole from myself.
3. Same as family issue. You might grow to resent them for robbing you of your choice. Honestly if they would abandon you they are shit friends. I love my friends flaws and they love mine. And my fellow trans friends are the best friends I have ever had because of a shared understanding. We might suffer but we suffer together. I can't imagine a world without them and I can't imagine them ever abandoning me.
4. I know plenty of tall girls. Cis and trans. Like I follow a girl on twitter who was an example of super muscle manliness and now she is so freaking hot and beautiful that I could die. And your voice can change with practice.

I'm not sure how much I can help because my thoughts and beliefs are probably as alien to you as your thoughts and beliefs are to me. If this is what you want you always have time. I just wish I started at your age. My family, friends, and faith restricted and robbed me of so much time and happiness. I suffered in silence while they pretended not to notice. I have scars because of them. Both mental and physical. Now I am writing my own story. Singing my own song. Dancing my own dance and I can't express how happy I am to finally be me. Will it be difficult life? Probably. But for the first time in a long time it feels like it will be MY life!

I hope you are happy with whatever choice you make.