Doug asks some good questions:
What is "sex"?
It seems most uses of that term indicate coitus, actual sexual intercourse.
I did address this briefly in the OP. Of course, the OP was fairly long and a precise definition of what actions constitute sexual immorality was not goal.
I have two initial thoughts which I hope and pray will help us think about this topic clearly:
1. We shouldn't ask "What's the most I can get away with?", but rather, "What is most pleasing to God and the best way to act?". I'm not saying that Doug is intending to ask "What's the most I can get away with?", but there is always a danger of starting to think that way.
2. Jesus addresses the deep roots and nature of various sins in the Sermon on the Mount. With regard to murder, He explains that even being angry with our brother is a sin like murder. And with regard to adultery, He explains that even looking at a woman with lust is included in the sin of adultery.
Matthew 5:27 "You have heard that it was said, 'You shall not commit adultery.'
28 But I tell you that anyone who looks at a woman lustfully has already committed adultery with her in his heart.
If we keep these words of Jesus in mind, they will help us through questions like the ones being asked here.
Can the unmarried even kiss?
So, there's no direct teaching on "kissing" in the Bible. But there are principles and there is godly wisdom. I'll share some thoughts, but understand that I'm not suggesting "rules", but rather I'm sharing my own understanding, trying to base it on Bible principles and wisdom:
1. Kissing while dating is likely to create increased sexual desire and arousal. I think that for many couples it will be easier to keep a boundary of "no kissing" than a boundary of "only kissing", because kissing so easily leads to carousing and sexual touching and more.
CSB Song of Solomon 2:7
Young women of Jerusalem, I charge you by the gazelles and the wild does of the field: do not stir up or awaken love until the appropriate time.
Stirring up sexual desires while dating someone is dangerous!
2. It seems to me that those who have saved their first kiss for their wedding day have not regretted that decision.
3. It wouldn't be alright for a married man to kiss another woman the way that couples kiss while dating. It would clearly be sinful. This is a strong indication to me that it is best to save kissing for marriage (I'm clearly not talking about the kind of friendly kiss one might give their grandmother, or that some cultures regularly use as a sign of friendship).
4. Passionate kissing may have been part of what Paul had in mind when he wrote:
CSB 1 Corinthians 7:36
But if any man thinks he is acting improperly toward his virgin, if she is past marriageable age, and so it must be, he can do what he wants. He is not sinning; they can get married.
It seems to me that "acting improperly" probably referred to some types of words or actions which could lead to sexual intercourse.
The OP guy, (if it is ok to speak that way?)
Yes, it's fine to call me the OP guy! Like most pastors, I've been called a lot worse!!
The OP guy, (if it is ok to speak that way?) indicates Christians would later regret any "sex" before marriage. I had a childhood sweetheart and one or two evenings a week we would kiss and kiss and kiss and nothing else. No trouble, and much pleasantness. (Neither of us decades later regret any of that.
Did you marry this childhood sweetheart who you kissed and kissed? I ask because it seems a little strange to me that you would know what she thought of your past kissing decades later if you had not married her. I'm not saying it would be necessarily wrong, just a bit unusual. If you married someone else it would at least seem awkward to me for you to have a discussion about past kissing with someone not your spouse. I realize this is a personal question, so don't feel obligated to answer or explain if you don't want to.
So I think the recommendation from the pulpit should be, kiss and only kiss.
Is it morally correct to make such a recommendation, and would it even be at all feasible?
I would certainly never recommend "kiss and only kiss" from the pulpit. I don't feel I need to draw an exact line for others. However, if I gave a recommendation, it would be to just hold hands and save your first kiss for your wedding day. But I would not judge a couple who kissed while engaged. I would gently warn against kissing before being engaged without making a judgment, but just warning of the real dangers involved. Does that make sense?
I think that saving your first kiss for your wedding day is the very best way to go.