No he can not. A step parent have no legal right to the step children. This could only happen if the parents consent to it. A minor can not choose but the court will hear their opinion at 16. They might not follow it though.
No, you cannot.
yep, if you are over 12 then you can choose what parent to live with
Yes they do,
16yo can not choose custodial parent at all. The court might listen to your opinion but that is it. And no, step parents do not have any legal right to the child.
If you live in the US it is.
nosee links
yes but she has to live with a parent
NO
No, you cannot.
nope, they have to be over 18
No, she has to be 18.