I'll leave the rest of your post to the others on this list, but I can answer this question:
What is it I am allowed to say about my gender identity or anyone elses and what is it I am not allowed to say?
You can say anything you want about your own gender identity. What you cannot (politely) do is contradict what someone else says about his or her own gender identity.
So if someone (anyone, not just a list participant) says "I'm a woman and I always have been", you should never say "No, you aren't." Nor "That person is only pretending to be a woman." Nor "He may feel like a woman but until he's taken a legal or surgical procedure, he's a man."
It's that simple.
Powers &8^]