Legal Question in Criminal Law in South Dakota

If you are subpoenaed (which you will be), you will have to go. The case will not be dropped if you don't show up; instead, the marshals will find you and bring you to court. They will use force if necessary. And if they don't find you right away, the case will be continued while they keep looking.

The Fifth Amendment is not just a convenient way to avoid testifying when you'd rather stay quiet. You can only invoke it when you have valid reason to think that a truthful answer would either result in you being prosecuted for a crime or be used against you in such a prosecution. Nothing you have written suggests that this is true.

You say the prosecutor won't "let" you drop the charges, but that's not how it works. The authority to drop a charge belongs to the prosecutor alone. It is never the victim's decision. The victims in domestic violence cases often ask for the charges to be dismissed, and it is very common for the prosecutor to refuse such a request.

If you want to help your boyfriend, you should ask his lawyer what you can do. You should also speak with a lawyer on your own if you believe you might get into legal trouble -- especially if you have made any false statements to the authorities.