Hi, AlphaPlus: I'm so glad you decided to post. You will receive a great deal of support here and won't feel like you're all alone in your trials.
Do what you feel you want to do in your heart but my advice is that you must take action and put together a plan. When you do, you will be proactive and not reactive. Make new friends as quickly as possible. That will ease the situation somewhat. Start putting together a plan for possibly moving out if you have to. You may not have to depending on the reaction of your grandparents. Then, and only when those pieces are in place, be honest with your grandparents. You will know where to go to from there. If you don't get baptized, you won't get involved in the DFng or DAng process. There probably will be some flak, however, from your JW friends and most probably you will be considered bad association. They may or may not react. Others on this board can give a better opinion on that scenario.
When you start taking action, you will feel better. You can always talk to us for support and, if you make an effort to make friends outside the congregation, you will have someone to at least socialize with. However, they will not be able to relate to the JW experience so be prepared for that. I know I wasn't and it was very frustrating for me to try to get them to understand. I post that part of my frustration on this board and simply keep my other social life on a laid back friendly basis rather than spiritual. The spiritual aspect of my life I work out here and in private. This takes time and it's okay to take a spiritual break, as long as you do not leave God out of your life entirely. Healing and trusting again will take time. God knows this. There will be time for you to recover spiritually and by all means get baptized in the appropriate way and not through the Borg. I would not want to discourage anyone from dedicating their lives to Jesus.
And by the way, there are plenty of nice young ones out there to associate with. Just continue to use your bible-trained conscience, however, and don't get involved with kids who are involved in things that you know go against God's laws. Get involved with more Christian friends. There are some on this board who will disagree with that but, IMHO, I can see no good coming from getting involved with the wrong crowd.
Graduating when you were 15???? That says something right there.
Hang in there and use that sharp noddle you got. {{{{{HUGS}}}}}
Trot