Can I help my 14 year old son emancipate himself from his father and stepmother

You might not be able to have him emancipated, that would be hard for so young a child.  But you might be able to get custody yourself.

Your question doesn't start to get into the basic facts that would have to be considered:  why the boy is with his father now, and what your situation is right now, as well as whatever it is that's going on in the father's home that your son needs to be rescued from.

If there's something seriously endangering your son's physical or emotional welfare, please talk to a lawyer as soon as possible, because if you can prove the problem, there is a chance that the court would take action.