BW, I was in a similar position. At 14, my parents took me out of school (high school, not enough control for them!), and shortly after, I was dunked. I was completely isolated and at their mercy.
Do what you need to do, love your horses, draw strength from your relationship with them (they are real, living and breathing, and have true emotions). from the joy of riding, and they will sense how you feel. You only have 2 years to go, if you have to, get baptized, worry about it later. It sounds like they will shun you when you leave the religion, whether you are baptized or not. Much love to you. xx tal