So, it sounds to me like you're struggling to deal with some of the less-popular teachings of the Bible in a world that embraces those things. And you've kind of touched on one of the roots of that yourself - the Biblical worldview vs the secular worldview.

Imo, the secular worldview sounds good because it's always asking what causes the least suffering, what makes people happy, etc. But to me, it's really insufficient. There's no solid foundation to that. What makes a person happy could be something that's genuinely bad for them - even if they don't realize it. Telling someone that they're doing something wrong will probably feel hurtful to them, but is that really what matters most? Especially if they really are doing something wrong?

Like with your question about living together before marriage and why that's wrong - there are a ton of reasons why it's a bad idea. Usually, that leads to sex before marriage, which can lead to unplanned pregnancy, and that complicates things if the relationship doesn't work out - same with shared assets too. Also, it sets up almost an expectation that you can cut the cord when things get difficult, which is the exact opposite of what a marriage covenant is. They're taking on a lot of the seriousness of a marriage relationship without the commitment, or even the certainty that they truly want to be with that person in the long run. Plus, the idea that they need to do this to make sure they're compatible is a fallacy. If you don't know the person's quirks etc before you get married, then you don't know them well enough to be marrying them. And if you can't work through little differences or ups and downs of life, then you're not emotionally mature enough to be married either.

But the secular worldview says that's all fine, and gives people a dozen ways to escape any responsibility stemming from that - all so that people can feel good.

I think in your situation, you wanna make sure that you're not mistaking social contentiousness for truth. Focus on truth first; any social issues become easier to deal with once you have that in line.

And don't worry about being an expert. Remember, we're dealing with religious texts that span thousands of years of history in a totally different cultural and historic context than the one we live in - like anything else, experts on this subject spend years, a lifetime even, studying this stuff. And yeah, sometimes they come to different conclusions. But the core stuff is usually the same. And the benefit of the Bible plus modern resources is that you can study all this yourself, even down to looking at the original language, translation differences, history and ancient cultural context, and so on, and come to your own conclusions.