First, understanding the Bible really does require an understanding of hermeneutics, or Bible interpretation, which you do not have.
It is wrong, exegetically to read back into the culture of the Bible, from modern culture. You have judged and condemned SoS because it doesn't meet with your 20th century views of morality. (I say 20th, because it doesn't seem like 21st!). Solomon lived around 1000 BC. That is 3000 years ago. He was Jewish, but a very Middle Eastern type of Jewish. He is not morally bound to behave like you expect a a repressed, 1950's man to behave. Sex within marriage was totally acceptable and so was writing about it. Which brings me to my second point. (Yes, sex within marriage is still beautiful and acceptable today!)
God inspired the whole Bible. That means the words of SoS are just as much a part of the Word of God, as admonitions to repent and turn from your sin are in the New Testament. If it was left in the canon, first in the Hebrew canon and then in the Christian canon, it is there for a reason. It does show that God created the love between a man and a woman and the passion two married people can have for each other. If it stimulates you, that is your problem, not God's. Perhaps you need to wait to re-read it till you are married? I know as a married woman of 36 years it does not offend me.
So to criticize God and/or the Bible because YOU don't like what it says, you need to examine who is God and who is not! Because YOU are not God. You do not have the right to criticize God for what he has written through his servant Solomon. When God saved me, he told me to read the Bible and believe it. Basically, you are saying you don't believe the bible because of what? Sexual love between a man and wife? How tragic you have set yourself up as judge/jury/executioner. Because that is NOT your place. I tell you, I was much more insulted by you, than I have ever been by reading SoS. And calling it porn? What sort of narrow minded background do you come from, anyway?
And regarding an older man marrying a young woman, as many others have said, the Bible does not give Mary and Joseph's ages. But, just so you know, my grandmother was 16 when she married my grandfather who was almost 30. They had a wonderful loving marriage, and produced 6 children, and 17 grandchildren. In fact, the only thing that was wrong with that age gap, is that my grandfather died long before my grandmother, and she missed him every day till she died. That is how many cultures operated. There was no going through school with same ages and then likely marrying someone from that cohort. Instead, they met people in their small towns and village, and were grateful for arranged marriages that gave the women financial security and the men wives who would care for their homes and bear their children.
I think you need to repent of this whole thread and your self righteous anger, coming out of your ignorance. You ask questions, and when people give you answers, you claim they have not? Why? Because they haven't agreed with you? Please note, not one single person on this thread agrees with you in any way, shape or form.
And if you really are not a troll, I would suggest you take your 21 year old ignorance, and learn what the Bible says about the wisdom of your elders, which is pretty much everyone on this thread. I do hope you will realize that in my eyes, you are just a child, and what sounds like a very spoiled child, demanding the bible conform to your expectations, or you will hate and turn away from God. Wait about 10 or 20 years, listen and learn, and then decide what to do about those 6 verses. By then, you may even realize that they truly are inspired and have incredible wisdom for marriage.