Hello Plix
It's really tough when family members don't support you or are not there for you. I have a couple of family members who treat me the same way you are being treated. It is a little heart breaking, but it is to be expected. Remember this is just as hard for them as it is for you. In my experience I have found that friends are more accepting as they have no vested interest in you, where your parents and sibblings do, as family tends to look to each other for support and in your case they may think you are threatening the family. Your mother is probably thinking that she may have somehow failed in your upbringing, and how is she going to explain this failure to others.
It would seem that you have an allie in your Grandmother so build on this, and with her, team up and start to win back those who may not accept you. Your mother may never accept, especially when she is falling to her religion to rebuff you, so you must prepare for this eventuality. Just keep plugging a long, after all she hasn't disowned you, so that's a start.
I wouldn't take a break for her either, as you may send the wrong signals. If you want to keep your family you have to communicate with family and even compramise, if that's what it takes, but remind them that this is who you are and that you will not change. Reasure them that you have not changed on the inside, and your love for them will not change even if they don't support you
My only daughter is having a hard time with my transition, she still loves me and everything but at her request, I've agreed not to dress as Stephanie, when she visits, until she gets her head around this. She asked me to bear with her while she sorts this out. She visits about once a month, so It's a small sacrifice on my part over the short term but it means that I will still be able to see my daughter and my relationship with her will continue.
You have to be firm in your convictions as there will be others who will not understand or support you, and eventually you will have to cut your losses and turn to those who do. You questioned "How can I do this without support"? You do have support, your grandmother, and for as much as we can the people here at Susan's
Don't give up on them or yourself.
Take care
Steph