No subpoena, don't show up for court. If you are subpoenad you can be held in contempt of court of you do not appear or answer questions. You do not have a marital privilege so you most likely will be forced to testify. You could take the 5th (right not to self incriminate) and refuse to testify; I would base it on not testifying because your testimony would conflict with your affidavit and open you up to criminal charges of perjury.
Well it seems as if the prosecutor has not prepared his witness for trial. Are you more concerned over the consequences to him than what happened? If you want to contact his defense counsel and offer to assist them in preparing their case, that can be done. The defense counsel may try to arrange a meeting with the prosecutor and hear you out. The case can be dropped by the prosectutor, but not by you. As I am often in Court call my assistant Dan London at 312-807-3990 to set up a private telephone consultation. At the consultation we can discuss the confidential details we need to craft a strategic plan. These details should not be broadcast over the Internet.
This is a general answer and does not address the specifics of your individual case. To give the specific answer you need our firm needs you to come in for a consultation.