If you are going to approach the seminary, you need to know who the spiritual formation director is. I would suggest that you have this matter in writing, and I would also suggest that someone accompany you to a face-to-face meeting with the spiritual director. Then write him a letter confirming what you have addressed in the meeting.
while you are at it, do not get into a discussion with the spritiual director over the phone; keep the phone call to the minimum of setting up a meeting. I would not even tell him what seminarian I was intending to discuss.
After that, you need to figure out how to get to his bishop/archbishop; he could be from another diocese than where the seminary is.
And before you do all of this, what will you do if this seminarian is dismissed for the seminary? What if, on being dismissed, he decides to stay in contact with your wife?
I would suggest that you do 2 things before you decide to see the spiritual director; 1 is to see an attorny who specializes in divorce. I am not suggesting that you want to go down the path; but if you escalate this, she may file. You need to know how to put yourself in the best position, particularly if there are nay children (custody is often won or lost before the filing).
2, go (by yourself) to see a good marriage counselor. You need some professional advice as to how to handle this with your wife. Failure to get that advice may lead you into a divorce, willing or not. She is going to see herself as attacked by you, that you just don’t understand, that he’s a wonderful, prayerful man of God who needs her special help. In other words, she is pgoing to react like most people do when they are out of line, and know at least subliminally they have crossed the line.
Your instincts are dead on. This situation, and your marriage, is merrily on the road to hell. How you handle it may well determine a lot of your future.