Mary was not unwed, she was betrothed to Joseph. Read Deuteronomy 22: 23-24, which clearly refers to a "betrothed virgin" as being a wife.
She was betrothed, but the pregnancy was sure a shock to Joseph, so this was clearly not the normal sequence of events.
Nope. The marriage had not been consumated. Joseph still had the option to put Mary away without marrying her.
That’s why Mary was said to be pledged to be married. Their intent was to marry, and their obligation was to act as if married, but Joseph still had the option to call it off.