I'm newish to trombone (two years) and recently learned the second octave Bb. I was just wonder since its so high is it a half step from middle C or and octave lower? Is it possible to get high enough that you go into Treble Clef on trombone?

on a second octave Bb, it is not really necessary to go into treble, tenor, or alto.
when it gets high (around maybe....G and above), you go into alto or tenor