Many of your end results are way out there, Tala, 10+ years ahead of you. I would start with science courses and see how you like and do with them. Lots of chemistry, biology, etc. I think vet schools are just as difficult to get into as med school as there are fewer accredited schools and as many students looking to get in so they only take the top ones. But there's a lot of classes that you might enjoy/find boring before you get to "work" in either field so I would explore how well you would like the education before deciding what you would like to end up as.

I would have the theater work as a side/elective thing for now, there are some really good theater schools and/or other parts of theater (one of my niece's is an engineer with a master's degree with Pixar Animation and another went to an exclusive North Carolina theatre school in stage management and lives/works in Los Angeles/Hollywood) if you find you are more drawn toward that area.