Expand on your statement: "who are in Christ, condemnation is lifted." Quote the scripture. I want to see if we are on the same page.
There are several Scriptures telling us that those who are in Christ are not under condemnation of the Law. I can think of these right off the top of my head:
Romans 8:1-4, Romans 5:16-18, 2 Corinthians 3:9
And the reason we are not condemned by the law, is not because the law itself has been done away (it hasn't) but because as we are in Christ, we fulfill the Law, through HIM!
The law, as a moral standard, still stands for those who are lawless and disobedient, etc. It is NOT done away for them, because they are not in Christ. The Law still stands to bring them to Christ.
The way this works, for instance in the Law concerning divorce and remarriage, is that IF we walk after the Spirit, we will operate in love, and we will not want to hurt, betray, stop providing for, those of our own household.
But if any Christian refuses to walk in the Spirit, and becomes selfish, and does NOT act in love, then he will not provide love and care for those of his household. It may go so far as to betray his spouse, via adultery and divorce.
And in that state, he is NO LONGER in Christ, and is again under the condemnation of the Law! He has denied the faith, and is worse than an infidel!
This thinking that the moral code of the Law is completely done away, so that we can do anything we wish (as long as we feel like we love them) and no longer have to remember the lessons taught us by our former schoolmaster, the Law, turns modern Christians into "worse than infidels".
It is true, that those who live in the Spirit, and walk no longer after the flesh, are above the Law. They don't have to have rules telling them not to divorce their spouses. But for those who walk after the flesh, they need the rules!
And the rules telling us what is godly have not changed.
All of the Law is contained in this: Love God above all, and love others as you love yourself.
If selfish humans instinctively could know what that looks like, they wouldn't need the moral code contained in the Law. I am not talking about those things contained in ceremonies, washings, clean and unclean, sacrifices... all of that, Christ has BECOME to us. Those who disobey the moral social code, aren't in Christ. They are outside the veil. They are not part of Israel.
But we who are now the true spiritual Israel (I speak only in the sense of Romans 9:6, and 1 Corinthians 10:18) walk after the perfect law of liberty IN CHRIST. Because IN HIM, ALL that which has to do with ceremonial laws and days, feasts, etc, are FULFILLED. We do not need to try to add to His perfect work there.
But in us, who are IN CHRIST, the righteousness which is contained in the Law, is lived out.
By love.
That's why true Christians don't divorce.
As you yourself said, what happens before one is born again, is washed away. He gets a clean slate. This only happens because the New Testament doesn't establish a new code of behavior. IF, however, the NT created a new set of rules, then ALL the old Testament is out the window.
In that case, all who are divorced and remarried would have to go find their first spouse, and return to them, even if they were living in the world at the time. NO remarriages would be valid, because Jesus said WHOSOEVER marrieth her that is put away, committeth adultery!
If you try to understand what Jesus taught, outside of the context of the Old Testament moral code, you end up with a much heavier burden of law than what God ever gave Moses.