There are several problems here, the least of which is hideous Marcionism. To characterise Jesus and the early church as being disconnected from Israel and her history is to miss the point. The story of Jesus is the fulfilment of the Torah (Matthew 5.17) and the apostles can speak against the law because although being a good, God given thing, it's purpose in the lives of God's people has been taken by Christians' unity to Christ and the dwelling of the Spirit in their bodies. Not because Israel was trying to earn her salvation and needed to be set straight, rather that Israel (and the rest of humanity and creation) has been redeemed in Jesus. The people of God are no longer marked by circumcision and other marks of Torah-obedience, but faith in the faithfulness of Jesus, so that whoever confesses that Jesus is Lord and believes in their heart that God raised him from the dead will be saved.
You would also be hard-pressed to separate Paul from the nitty-gritty of reality. Not just an intellectual idealist, Paul is concerned as much as the Law is in living out life rightly. From circumcision to sex and money to political authority, Paul has more to say than a justified by faith free-for-all how to live life. By the same token, to portray the Law as being just about works and not love is a vulgar misrepresentation because it is love itself that lies at the heart of the Torah: "And now, Israel, what does the Lord your God require of you, but to fear the Lord your God, to walk in all his ways, to love him, to serve the Lord your God with all your heart and with all your soul, and to keep the commandments and statutes of the Lord, which I am commanding you today for your good?" Deuteronomy 10.12-13 (cf. Deuteronomy 10.12-22, 6.1-9 and 7.7-16).
As Oliver O'Donovan helpfully states:
"On two occasions in the writings of Saint Luke we are told that a crowd which heard the preaching of the gospel asked, 'What shall we do?' The answer was different in either case. John the Baptist (Lk. 3:10ff.) responded with some specific moral counsel: 'He who has two coats, let him share with him who has none; and he who has food, let him do likewise.' Saint Peter, on the other hand (Acts 2:37-38), replied, 'Repent, and be baptized every one of you in the name of Jesus Christ for the forgiveness of your sins; and you shall receive the gift of the Holy Spirit.' It would be mistaken to interpret this difference in terms of a contrast between law and gospel, between preaching before and preaching after the coming of Christ. John the Baptist was quite capable of giving the reply that Saint Peter gave (apart from the name of Jesus and the promise of the Holy Spirit), while Saint Peter could easily have replied as John did..." Resurrection and Moral Order, pp. 182-183.