First of all: There is no such thing as "pressing charges." This is a common misconception. Criminal charges are investigated by the police and referred to the District Attorney, who decides whether to file a case or not. Private citizens, including crime victims, can contact the police to report a crime and can cooperate with the DA in making their case, but that's all they can do. They have no legal authority to compel (or to refuse to allow) a criminal prosecution.
That said, crime victims do have certain rights under the Oregon constitution. To take advantage of these rights, you need to be certified as a victim by the court. (It's not clear from your question whether you were the victim of a crime, but I assume from your use of language that you might have been.) These include the right to be present at critical stages of the proceedings, to be consulted about charging decisions (but not to unilaterally make those decisions), and to resist discovery attempts from the defendant. But they do not include the right to refuse to appear for a subpoena. If you have been summoned by a subpoena, then legally, you must appear. Failure to do so could result in a warrant for your arrest, which the Michigan police forces could execute.(An incorrect address does not invalidate the legal force of the subpoena.) Furthermore, if you appear as a witness in court, you are required to tell the truth - you cannot decide "not to testify against" anyone. You do have the right to request reasonable fees and reimbursement for your travel - which, if you're coming from Michigan, could be pretty substantial.
Obviously I don't know just what all happened, but I would suggest that you contact an attorney in Oregon and see if you're eligible to receive victim status in the case. This would give you a lot more options in dealing with the DA, and grant you a voice in the process which might compel them to dismiss it if that's really what you want.