Unfortunately no exegesis is going to settle things, because the real question goes beyond specific passages to how we treat Paul’s letters. The passages that might involve premarital intercourse aren’t actually specific teachings. He doesn’t say “I have it from the Lord …” on this topic. Rather, a couple of passages show that Paul accepted standards of 1st Cent Jews on this topic. (The issue is Paul. Jesus didn’t say anything on the topic.)
So the question is: Does accepting Christianity mean that we accept 1st Cent Jewish culture? If not, where can we diverge? In the 1st Cent, Jews got married earlier than today. If someone didn’t have the gift of celibacy, the simplest solution was to get married. (1 Cor 7:9) But today that often isn’t the best solution. Is this an area where we’re permitted to differ from Paul’s culture?
[One exegetical note. I Cor 7:9 is the clearest reference of Paul to this topic. But in 1 Cor 7:10 he implies that the section including 7:9 was his own opinion, not the Lord's. This is very rare in Paul's letters. We might want to take it seriously.]
People often cite data that people who cohabit are more likely to divorce when they get married. But it turns out that this difference disappeared when you control for the age when they start. (
https://www.theatlantic.com/health/...-step-toward-marriage-not-a-rebellion/284512/) In today’s society, marriage and cohabitation both work better if you wait until your 20s. Thus Paul’s recommendation, which I’m sure was right for the people he wrote to, may not be helpful today.
What should you do before it’s appropriate to get married? This is a question Paul never faced. He did understand that celibacy is a gift that not everyone had (1 Cor 7:7)
I looked back over my own Church’s detailed report on human sexuality, from 1991. It never actually justifies premarital intercourse. But it assumes it will happen. It says we should be providing guidance to help kids from getting pressured into doing things they aren’t ready for. The data I know says “just say no” doesn’t work. Good sex education reduces teen pregnancies more than abstinence-only approaches. (There are many studies that could be cited. E.g. see
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3194801/. The real shock in this report was how our statistics compare with other developed countries. Our prudery seems to be backfiring.)
The fact is, Christians today don’t typically remain virgins until marriage. 41% believe cohabiting before marriage is a good idea. (
https://www.barna.com/research/majority-of-americans-now-believe-in-cohabitation/) Even more actually do it.
http://religion.blogs.cnn.com/2011/09/27/why-young-christians-arent-waiting-anymore/. The links go nowhere, so I’m not citing the underlying research, but here's what their summary says: “While the study’s primary report did not explore religion, some additional analysis focusing on sexual activity and religious identification yielded this result: 80 percent of unmarried evangelical young adults (18 to 29) said that they have had sex - slightly less than 88 percent of unmarried adults, according to the teen pregnancy prevention organization.”
We have a long period during where there is dating, something that wasn’t present in Paul’s time. We provide little guidance for it, because of course Scripture would have no reason to talk about how to do something that wasn’t part of 1st Cent life, and the Church’s main position is “don’t.” But I believe there are better and worse approaches. Indeed I think kids get pressured into having sex when they shouldn’t and probably even don’t want to. But by not giving advice for the kinds of relationships they're actually in, we’re not helping kids deal with this.
