There are 2 separate issues in your question. The plaintiff on a restraining order (a civil matter) can have the order vacated anytime; all you have to do is go into the court and tell the judge that you want to vacate the order. The victim witness advocate and the judge may try to talk you out of it, but there's nothing they can do to make you keep the restraining order open if you do not want it.
A victim on a criminal complaint does not have the same power to "drop the charges". Once a criminal complaint has been issued against the defendant, only the district attorney's office can drop the charges unilaterally. While in many (but not all) cases, if the victim does not want to testify against the defendant, the prosecution cannot proceed to trial against the defendant, most prosecutor's offices will not dismiss domestic A&B charges (even if they know the victim is not on board) until the day of trial. In some cases, the prosecutor does not need the victim to testify to prove it's case against the defendant. It's important that the defendant speak with a lawyer to determine if his case falls into the latter category. Good luck.
You may vertainly vacate a restraining order whenever you like by requesting that the court do so. A restraining order, under chapter 209A, is a civil order and that is why you can vacate it. However, once a criminal complaint is filed, is is not like a civil complaint where it is You v. the Defendant. Once the complaint issues, it is Commonwealth v. Defendant and it is up to the Commonwealth, represented through the DA's office that is the only entity that can decide to dismiss a criminal complaint.