Don't have much time today, so I will be brief. There is plenty of evidence to show that Isaiah's reference to the "Suffeirng Servent" is about Israel and not some future God-man.
Don't unbelievers believe in prophecy?
I don't know. You need to ask an unbeliever. I do not deny God, so you must have me confused with someone else. If you don't know something, that is not a denial.
You said you were an agnostic..
The church has always read that Scripture as prophecy, only agnostics dont