How can I enhance my voice?

I want to be able to sing higher, but Im still young. A couple of months ago, I couldn't sing higher than I could speak. but now, (on a guitar) I can sing from C standard (if you lowered the E string to C, so drop C), up to the 11th fret on the high e string. Before, it would just crack, but now, if I try to go higher, I just get Eb, and It sounds weak. So I can't sing this note, but it feels different. Does this mean that is my limit? Or is it something else? Also, my voice just sounds nasally, and it occasionally cracks very slightly. the More I sing, the better it gets, but how can I get a smoother voice like Geddy Lee? Yet, sound grungy like Kurt Cobain, or even sound thrashy like James hetfield On "Ride the Lightning" because his voice sounds a bit Icy. i can sing at the octave, But I want to sing higher like Rob Halford or someone. Any suggestions