Is the gospel a new law?
I think your real problem comes down to something else. You think of the gospel as a new law. You know that the old law is far above your reach, and that it condemns, but cannot save you. But you think, perhaps, that Christ came to make the law easier, to lower its demands, to make it (as some say) an evangelical law, with milder terms, suited to the sinner's weakness. No one is strong enough to be perfect. So Christ changed the law and now I save myself by believing.
This is blasphemy. And you only have to think for a moment to see it. For it means that the former law was too strict; that is, it was not holy, and just, and good. It denies also Christ's words: that he came not to destroy but to fulfill the law. God has only one perfect law, and it is perfect: love God and man. A milder law must mean an imperfect one; a law that makes God's one law unnecessary; a law that gives countenance to sin. Will obedience to an imperfect law save the breaker of the perfect law? But faith does not make void the law; it establishes it.
It is by a perfect law that we are saved; else it would be an unholy salvation. It is by a perfect law, fulfilled perfectly that we are saved; else it would be an unrighteous salvation. The Son of God has kept the law for us; he has magnified it and made it honorable; and thus we have a holy and righteous salvation. Though above law in himself, he was made under the law for us; and by his spotless life, as well as by endurance unto death of that law's awful penalties, we are redeemed from the curse of the law.
"Christ is the end (the fulfilling and exhausting) of the law, for righteousness to every one that believes." FOR CHRIST IS NOT A HELPER, BUT A SAVIOUR. He has not come to enable us to save ourselves, by keeping an incomplete law; but to keep the complete law for us. Now the law has no penalty for anyone who agrees to be the debtor to the law keeping of Christ.