You should consider looking into emancipation under Arkansas law. This usually requires demonstrating to a judge that you are employed and financially able to support yourself.
It is my understanding that the minimum age to obtain a marriage license without court or parental permission in your state is 18. However, emancipation also results from marriage, if your boyfriend is willing and you are able to obtain a license under Arkansas law.
Your father may also attempt to gain custody without a lawyer.
I hope your grandparents survive until you are 18. However, if that does not seem likely, they should look into setting up a trust for your benefit, such that the house remains in trust until you reach the age of 18 and your mother can't interfere with your decisions or try to force you to sell the house.
These are issues you (and your father and grandparents) should discuss with a licensed Arkansas lawyer.

