I really want to be a stage manager for live theatre?

You'd actually want to major in Stage Management, but don't worry yet. Finish your Bachelor's degree and then get your Master's in stage management (and do any plays you can in the mean time) In graduate school there's a lot more emphasis on working with unions (and their regulations) along with learning to call different types of shows (dance, musicals, plays, operas, etc..) The MFA program where I went to graduate school is a two year program for stage management.