I agree with you that it really is the crux. I agree that that we cannot parse the law. I agree that Jesus did stated that not a letter of the Law would pass away until it was all completed.
The thing I've tried - so far without success - to get people to focus upon is the fact - not the speculation, the actual written fact, that there are TWO sets of laws at work, and that only ONE set of those laws applies to Christians.
"The Law" when Jews such as Jesus or Paul, Peter or the Apostles refer to it, is a translation of a Greek word which is a translation of the Hebrew word "Torah". It does not refer to all laws, all rules, all regulations everywhere. It refers to a very specific body of rules, given as a contract by God at a specific place (Mount Sinai) to a specific people (Hebrews who were there). On its own terms it only applied to them and their descendants, and it only ever did.
On its own written terms the only thing that the Law EVER promised was that the people under the contract, the lineal, circumcised descendants of Jacob who were standing at Mt. Sinai would receive and securely hold a family farm in the land of Canaan, and only for as long as they obeyed The Law.
That is IT. That is ALL that "The Law" EVER promised, or EVER stood for.
Now, Christians all the way back have been misunderstanding this fact - which is a written fact - the Torah SAYS what its terms are, who it applies to, and what they get.
Complete obedience to the law, PERFECT obedience, never, ever promised eternal life. It did not before Jesus, and it did not after Jesus either. Jesus completed The Law, for the Jews, by demonstrating what it was pointing towards. However, Jesus said he did not destroy The Law or change The Law, that it would never be changed until the end of the world.
What THAT means is that The Law NEVER became something that had to do with eternal life, or Heaven, or anything other than its original terms: Jews, only, who follow it all, in this life, only, get a physical farm in the land of Canaan, only, in this life, only. There is no covenant that says that if one follows the whole law of Moses, one is saved and goes to Heaven. SCRIPTURE NEVER SAYS THAT. NOT EVER. It doesn't even SUGGEST it.
The Law, properly stated, is ONLY the Law of Moses, and the Law of Moses never promised ANYTHING regarding life after death. The Law of Moses only EVER applied to Jews, in THIS life, and it only EVER promised a FARM - a plot of farmland - in a specific land - Israel - during THIS life only. And only if it were all followed. Nothing more and nothing less.
So, when Christians talk about picking and choosing in "The Law", they may as well be talking about choosing which of the laws of the Japanese Empire they are going to obey. If they're not also Japanese, the laws of the Japanese Empire have NOTHING TO DO WITH the laws that Christians are to obey.
What furthers the confusion is that the early Christians, almost everybody that Jesus and the Apostles addressed, was ALSO a Jew, and so The Law - of Moses - actually MEANT something TO THEM. But it NEVER MEANT ANYTHING to a Gentile, neither before Jesus nor afterwards. The Ten Commandments are included in this. The Ten Commandments given at Mt. Sinai never ever applied to anybody but Jews. They did not apply to Christians, and Jesus did not bring the Ten Commandments to Christians.
Rather, some of the laws that God gave all of mankind BEFORE Sinai - the law against murder given to Noah - that still applies (NOT because it's one of the Ten Commandments, because the Ten Commandments apply to nobody but Jews - God included that general law in the Ten Commandments, but its authority over US is because God gave it to the world).
If a law is in the Torah - The Law - it doesn't apply to us at all, never did, and never will. THat was a contract made between Hebrews and God, and we're not parties to it. NONE of it applies to us. It's not a matter of picking and choosing. NONE of it makes any difference. Your neighbor has a contract with his bank, a mortgage on his house. Those terms and conditions are between him and the bank. If YOU fully do everything required under his mortgage, follow all of its restrictions, etc., you get NOTHING, because it's not YOUR mortgage. It's his. You never have had, do not have, and never WILL have any rights under, or duties under, your neighbor's mortgage. That contract binds HIM, but it has NOTHING TO DO WITH YOU.
That that's "The Law". It's a contract between Israelites and God. NONE OF IT ever applied to Christians, unless they were Jews.
Most of the Christians in the New Testament WERE Jews, and sorting out for themselves that the Law of Moses had NOTHING TO DO with being a Christian was hard for them, for it meant effectively apostasy from their cultural covenant. Many tried to straddle the two worlds, and insisted that Christians who were Gentiles had to become Jews, meaning that Christians were under The Law.
But Jesus never said anything remotely like that.
So, the first big concepts are that "The Law" when called that, in the New Testament, MEANS the Law of Moses, and that the Law of Moses is COMPLETELY INAPPLICABLE to anybody who is not a party to the contract. Gentiles are not. They don't become parties by becoming Christians. It only applies to Jews. And even if JEWS follow The Law (which is The Law of Moses) perfectly, that does not have ANYTHING TO DO with life after death and final judgment. Those things are not part of The Law, and Jesus didn't graft them onto The Law. Quite the opposite: he said that The Law would not change AT ALL until the end of the world.
Jesus' New Covenant is COMPLETELY NEW. It is not something grafted onto the Law of Moses. That's the whole point of Jesus' parable of the old and new wineskins. Christianity is new wine, and it is placed in new wineskins. It is only related to the Law of Moses because the Law of Moses mentally prepared the Jews to be the standard bearer for the New Covenant.
I keep harping on this point because it is so important. The New Testament recounts JEWS struggling with what to do with the old Law, the Law of Moses, and coming to different conclusions, referring back to that law for inspiration, but finding new things and issues. It shows us how the Apostles, who were all Jews, came to the realization that The Law was dead as far as Gentiles were concerned. But even the Apostles, being Jews, were not particularly skilled lawyers. They grasped that things were different under the New Covenant, but none of them ever spoke out in the Scriptures the REASON why Gentiles did not need to follow The Law: because they were never subject to it in the first place!
This would have been hard for a Jew to admit, because the whole Jewish world was structured around that law, and the Jews had grafted on top of that law their own traditions of life after death and resurrection, but unless one includes books such as Enoch and the Maccabbees in the Old Testament, one cannot find Old Testament Scriptural promises of eternal life that have any clarity. Certainly one cannot find any such things in the Torah ("The Law").
And this brings us to the second major point, "The Law" in the New Testament, that we are freed from, is specifically the Law of Moses, the Torah. We are NOT freed from LAW as a general principle. For Jesus also gives an extensive body of law under the New Covenant, law that must be obeyed on pain of hellfire. Forget the farm in Israel - what's at stake under the law of the New Covenant is eternal life.
There is "The Law", which is the Torah, the Law of Moses, and it does NOT apply to Gentiles (and never did). THIS is the law that is called "The Law" by the New Testament figures. But there is ANOTHER Law in the New Testament, the Law of Jesus. It consists of his precepts and the stern warnings he gives about hellfire for certain acts of commission and omission. Those laws are different from The Law, but they are much more important, powerful and impressive than the mere old "Law", of Moses, for the Law of Moses only ever applied to maybe 1% of the world's population and not to anybody else. The law of Jesus applies to EVERYBODY, whether they believe it or not. THAT law IS mandatory. If one breaks IT, one faces damnation unless forgiven.
So, when I see these efforts to muck around in the Law of Moses, I try to set the record straight based on the Scriptures themselves. It clears so much freight when one realizes that the Old Testament does NOT provide law for the Christian. It clears away some really dangerous delusions when a Christian realizes that he IS under law - the Law of Christ - just not under "THE Law", which is the Law of Moses.