Ahhh... you are too hooked on accents
"Sí" is the affirmation, "si" is a conditional.
Estoy:
Estoy feliz - I'm happy.
Estoy en México - I'm in Mexico.
Soy de feliz - I'm from happy.
Soy feliz - I'm happy.
Soy de México - I'm from Mexico.
Soooo... the difference between "estoy feliz" and "soy feliz", its the time sense. "Estoy" refers to "right now", an inmediate present. Meanwhile "soy" refers to a definitive, natural, sense, like "always".
Right?
Phew.