Hi Letty,
Your story is so heartbreaking. Your feelings for your bf are perfectly natural, as is your desire for him and the pleasure you take from your explicit messages. The sexual tension created by JWs and their policy of extreme abstinence is so toxic and impossible for most kids to abide by. Please don't beat yourself up too much, everyone else is going to do that for you, so stay strong.
My advice would be to ride it out in the short term, say what you have to until you can find some part time work, get into school, find some roommates and become self sufficient.
You're a good kid, your heartbreak at being condemned by your family and yours years of hard work are a testament to that. If you do leave the organization, I think you will have a happier, more complete and fulfilling life in the long run. But in the short term there is going to be a lot of pain. If you can afford it, I recommend seeking counselling of some kind to help you get through the first few years. My cousin was DFd and completely disowned by his family and is still so full of anger and hurt. He and I only recently reunited and I wish I'd been there to help him through that time.