I have posted my biblical references every time we've gotten down to cases in this discussion. Kindly return the favor. To what verses do you refer? I am not inclined to scour the New Testement to make your argument for you.
Oh, and do be sure to point out to me how these references you are going to offer up resolve the dilemma of the fellow we are talking about, whose been beseeched to impregnate his neighbor's wife, and wishes to follow God's law on the question, as soon as you can advise him properly.
You seem like an educated guy which is why I didn't feel obliged to provide links. Some of the most famous NT -- and OT -- passages involve adulterers/adulteresses. There is the He who is without sin incident and the woman at the well. to cite two.
The NT is largely a rejection of legalism -- although as you point out -- not the law. Adultery remains wrong.
Concerning the situation you described, those involved would have to account for their actions before God. If they can, they can.
A better and, more common, example of apparent Biblical inflexibility concerns divorce which the Lord equates with adultery.
You can posit the far more realistic situation in which a woman who divorces the fellow who has been beating her every night and goes on to marry a nice guy who will support her kids, then ask if she has committed a sin.
Now, an absolute saint might leave the husband for safety's sake, pray for his soul and raise the kids on her own. A weaker person might not. The same chapter says Blessed are the merciful, for they will be shown mercy. and two chapters later comes the warning about judging ohers.
According to the Bible is divorce adultery? Yes. Is adultery a sin? Yes. Can God still love those who committ adultery? Yes, obviously.
You might also want to consider what Matthew 5 says about looking at a girl with lust. That was one of the verse I had trouble accepting when I first began believing. It soon made perfect sense. You look at a girl and feel attraction you are human. You look at a girl and start scheming of a way to take her to bed forgetting that she is human too, you are comitting adultery.