Estoy el lider de este pais....,surely correct!
You cannot say Estoy el líder... because you cannot use estar before nouns.
soy - permanent (hombre)
Estoy - (transient) lider/job
Right. With Está it sounds like "the leader of this country is in" as in "in his office right now"
Why must it be "Yo soy..." rather than simply "Soy el líder..."?
Either should be acceptable. If "Soy el líder..." isn't accepted, it should be reported.
Duo only accepts male leaders. I tried "soy la lider de este pais" and was down voted, but la lider is perfectly acceptable Spanish.
Wouldn't soy el lider mean a monarchy or dictator as these are the only ways how being a leader is a permanent state?