Dealing with betrayal by people, especially family members is never an easy thing. For me, I have found that being thankful for what I actually do have in my life is not an easy task either, but does help get my heart on the right track...even in the midst of hardship. Despite all the crappy emotional stuff i may go through on a daily basis, I try to remember i have a roof over my head, plenty of food, hot running water, 2 people that actually care about me, and a computer with internet access so i can find support from websites like this one.
The most obvious blessing i see that you can be grateful for is having such an awesome grandma!! She is your rock right now. Of course Jesus is THE rock, but you get what i'm saying. She seems like someone you can trust and rely on and having a close grandma is a good thing. Of course, having friends at this time in your life is also good, especially ones whom you can trust and talk about your feelings with. I don't know if your school has any groups like Young Life or whatever, but maybe you can get involved in something like that for more support. It sounds like you live in a small town, but there has to be some kind of cool youth group in a church somewhere nearby. Maybe you can do a search online for one and get your parents to take you there.
In the meantime I hear you say that He's all you have left to hold onto. And maybe right now, He is. We can't understand why we are where we are at any given moment, but He does. I've felt this way many a time and these are the times I have grown the most in my faith. Sometimes i personally have felt He has taken all my known comforts and friends away for a reason...not to torture me, but to help me grow in a way I could've never seen before. In hindsight i see that clinging to Him in my darkest moments has been worth the journey. I understand Percepi's "pick yourself by your bootstraps" idea, but don't forget He's also right behind you in this...helping you along. It's really up to you now...how much you want Him to help with your bootstraps. And the more you let Him in, the more your tree will bear fruit and bless others as well. Don't give up on prayer and meditating on His word. Hang in there! He's with you. Your journey has just begun.