Teen, definitely. I'm not sure about pre-teen.

But keep in mind that pretty much all women/girls were married off pretty much once they were physically fertile in those days. You can't judge it by today's standards.

Additionally my understanding is that Joseph was either already widowed or had never married and his idea was just to take Mary as a "wife" to support her because no one else would and he wasn't even intending to expect any marital relations from her. However I don't remember where I got this idea from so it very easily could have been some revisionist teaching that isn't supported by the actual Church.

Probably between 14 and 16. But nobody knows for sure... That was a common age for marriage (for women) at that time.