Once upon a time when the police came to the scene of a domestic disorder and the couple didn't wish to prosecute, the police could just calm the situation down and leave without making an arrest. For years now, because domestic violence has been in the public limelight, that is no longer the case. If the police are called to the scene, whatever their private feelings about the incident and despite the wishes of the people involved, someone will go to jail. Laws have eliminated police discretion in this area.
Worse yet, once the state gets involved, this case is not yours to drop. It belongs to the prosecutor who can choose to go forward whether you want to or not. That's the bad news.
The good news is that in most cases the prosecutor cannot win a domestic case without the cooperation of the victim, who is you. So the first thing you need to do is to make the prosecutor aware of the fact that there was no physical harm done by your husband, that you don't want to pursue the matter any more, and that you wish all charges dropped against him. If you can convince the DA that you are not at risk from your husband, he has the power to drop the case.
If the DA refuses to help you, one thing you can do is to contact your husband's lawyer and tell him that you've been trying to drop but the DA won't let you. Ask him what you can do to help. He can bring the fact that you don't want to go forward to the attention of the judge, who can put pressure on the DA to get rid of the case. That can be helpful. Even if it is not dismissed, the DA may make a very favorable disposition to your husband.
Another thing you can do is just to ignore the DA from there. He NEEDS you to make his case, so if you don't talk to him over the phone, don't cooperate by coming in or talking to him when he wants you to, sooner or later the case will probably have to be dismissed because the state doesn't have their chief witness -- YOU.
When I say this, I am not telling you that you should ignore a lawfully served subpoena. If you are personally served (not by mail, phone or email) but by a live person who hands you an order to appear, you have to honor that or face arrest. Then you could show up with a lawyer and simply refuse to testify against your husband. If you are never personally served, however, you are not risking contempt charges, and the case will eventually have to go away.