I second Alex. Even though frustrating, you seem to have a solid support group, whether they fully grasp it all yet or not. I went through a similar situation years back in my mid teens, with a few friends whom I'd known since childhood. They'd ask questions like "So, when you're 18, you'll just get another guys penis that wants to be a girl?" Which, being completely ignorant myself, I thought that was the trade-off.
All I can suggest is leading in them in the direction of some solid material online, of what being a ftm entails. Sometimes your experience in itself isn't enough to help others understand. On the bright side, these same friends I mentioned above, 10+ years later, are still the closest, most understanding friends I could ever ask for. Time, patience, and knowledge will bring them a long way. The love is already there, which is most important.