Anyway, I closed by raising the question: "Do Matthew 18 & the other passages on church discipline apply to those in positions of spiritual authority - pastors, priests, elders, etc?"
You better believe it, bucko.
Yes, with a slight (and I do mean slight) qualification to take into account 1 Timothy 5:19 (NAS):
Do not receive an accusation against an elder except on the basis of two or three witnesses.
In practical terms, anyone can have a problem with me as a pastor, due to my behavior or their perception of my behavior. They have a responsibility to confront me as a brother in Christ about things that are wrong. If I'm unwilling to deal with it, they are able to bring others into the situation in order to resolve it. In order to accuse me of wrongdoing & unrepentant behavior, there needs to be 2+ people who have witnessed this... which will happen as a part of the Matthew 18 process.
Please don't take this as me posting an "Rabbit Hunting Season" sign on the office door of your pastor. At the same time, this should be a bucket of cold water dumped on the crappy theological dodge of ministers waving around "touch not the Lord's anointed" as a cover for sin. (BTW, Psalm 105:15 must be set in context to be properly read - the psalmist is writing about how God has been & is protective of the Jewish people!)