You're probably not overreacting, however, give the prof the benefit of the doubt and talk to him tonight. Until you know what was so urgent to him, you don't know if he's just being a freak. However, if it's just about the one minor missed assignment, yes, talk to the dean.
As for his beginning stuff, he sounds like he's used to high schoolers, not college students.
I've never had a prof be that ... involved.