Do You Think This Is a Good Idea For When I Finish High School ?

Art Institutes are not granting actual degrees. You'd have to go earn a bachelors degree in physics from a real college before you can apply for a graduate program in astronomy. The art job is just wasting your time, since the PhD in astronomy will take 8-12 years and then you'll need another 2-6 in postdocs before getting a real job (or leaving the field, because there are more people who want to work in the field than there are jobs for them).