1. It should be the leader of leaders because
First, you and they are already leaders of some organizations .
and you didn't mention them before. I mean especially in your previous sentences.
So, in this case, you shouldn't mention them as "the leaders".
Second, among them,who were leaders, you are the special leader meaning you are their leader.
This is the second reason you should express you as "the leader".
In conclusion, the first answer to your question number 1 should be "the leader of leaders:.
Unfornately I don't know the answer to number 2. I'm really sorry I can't give you the other answer to the question.
I hope you are satisfied with my answer. Thanks.