So are Psalms 119:142 and 2 Timothy 3:15-17 wrong? At the time Timothy was a infant, the only Scriptures that had been written yet were OT Scriptures, so Paul was primarily saying that God's law is God-breathed and profitable for teaching, for reproof, for correction, and for training in righteousness, that the man of God may be complete, equipped for every good work. Furthermore, according to Deuteronomy 13:4-6, the way to tell that someone was a false prophet was if they taught God's people against doing what He had commanded, even if they performed performed signs and wonders, so God's law was given as the standard of truth. According to Acts 17:11, the Bereans were praised for apply this standard by testing everything Paul said against OT Scripture to see if what he said was true. If Paul had tried telling them that Leviticus 11 was cancelled, then they would have known that he was a false prophet and rightfully disregarded what he said instead of accepting it.
In Romans 6:8-14, the law that we are no longer under has to do with sin and death no longer having dominion over us, so the law that we are not under is the law of sin and death. In Romans 7:12-Romans 8:2, Paul said that God's law was holy, righteous, and good, that it was the good that he sought to do and delighted in doing, but contrasted that with a law of sin and death that was working within him to cause him to not do the good that he wanted to do, so the law of sin and death is the opposite of God's law. God has no need to deliver us from obeying His instructions for how to do what is holy, righteous, and good, nor should we even want to be delivered from them, but rather we should likewise day delight in obeying God's law by faith (Psalms 1:1-2, Romans 7:22).
In the Romans 7:1-4, Paul was not using an analogy where everything in the example is represented by something else, but rather he said he was speaking to those who knew the law, so he was using an example from the law to illustrate his point. We can't be represented by the woman because we are dying to the law and it is her husband that died and we can be represented by the man because we are the ones who are set free to belong to another. When the woman's husband died she wasn't set free from the law so that she could now freely commit murder any do everything else the law prohibited, but rather she was only set free from the aspect of the law that would penalize her if she were to live with another man while her husband was still alive. If we are dead to the law, then it can't penalize us, so being dead to the law is not a status of being free from obeying it, but a status of being free from its condemnation, which is the point that Paul was concluding from in Romans 8:1. In Romans 7:6, is specifies that we died to that which held us captive, so it is again referring to the condemnation of the law, not to its holy, righteous, and good instructions. God's law is a law of liberty (Psalms 119:145, James 1:25) and it is sin in transgression of God's law that puts us in captivity.
What was nailed to crosses were the charges against someone (Mark 15:26), not the law itself, so they didn't have to legislate new laws every time someone was crucified. This fits perfectly with the concept of Messiah being our kinsman redeemer who died on the cross for the penalty of our sins and to set us free from captivity to sin, but does not fit at all with him dying to redeem us from the law. In Titus 2:14, it does not say that Messiah gave himself to redeem us from the law, but from lawlessness.
In 2 Timothy 3:16-17, it refers to OT Scriptures as being profitable for equipping us to do every good work, so does it make sense to you to say in Ephesians 2:10 that we are made new creations in Messiah for the purpose of doing good works and then a few verses later say that Messiah abolished his instructions for how to do good works? Rather, what he abolished were man-made ordinances, such as mentioned in Acts 10:28 that forbade Jews from visiting or associating with Gentiles, which were actually against God's word (Leviticus 19:34). We should be careful not to mistake something that was against obeying man's laws and being against obeying God's commands.
Romans 15:18-19 For I will not venture to speak of anything except what Christ has accomplished through me to bring the Gentiles to obedience—by word and deed, 19 by the power of signs and wonders, by the power of the Spirit of God—so that from Jerusalem and all the way around to Illyricum I have fulfilled the ministry of the gospel of Christ;
In these verses, fulfilling the gospel does not refer to doing away with it or to making it no longer binding, but rather it refers to fully teaching obedience to it. Similarly, in Matthew 5:17, fulfilling the law does not mean to make it no longer binding, but rather it refers to fully teaching how to understand and obey it, which is precisely what Messiah then proceeded to do in the rest of the chapter. Your understanding of fulfilling the law is essentially the same as abolishing it, which Messiah contrasted with fulfilling it.
The context of Mark 7 is a discussion with Pharisees about whether people could be defiled by eating food with unwashed hands (Mark 7:1-4) and at no point did the conversation jump from being about a man-made ritual purity law to being about God's dietary laws, so Messiah was just countering the man-made law. His statement at the end of the conversation in the parallel account in Matthew 15:20 confirms that he was still talking about not being defiled by eating with unwashed hands.
Mark 7:19 is a rather difficult passage to translate because there is no "thus he declared" in the Greek, and a number of translations do not say that he declared all foods clean. However, even if I were to grant that is correctly translated, it would still not support God's dietary laws being done away with. For starters, when one Jew is talking to other Jews about food, they are not talking about the things that we consider to be food, but the things that God gave them to as food in Leviticus 11 and Deuteronomy 14, so eating pork would never have even come to their minds. However, even if I were to grant that they were talking about everything that could be eaten, including human flesh, the word translated as "clean" is only used in the context of ritual purity, so at most he was saying that all foods were ritually clean, which is again in line with the context of the discussion.
Messiah had just finished calling the Pharisees hypocrites for setting aside the commands of God, so if he had set aside God's dietary laws just a few verses later, then that would have made him an even bigger hypocrite. Furthermore, doing that would put him in violation of Deuteronomy 13, which would have made him a false prophet and disqualified him from being the Messiah. According to Deuteronomy 4:2, it is a sin to add or subtract from God's law, so he would have also been sinning, which would again disqualify him from being the Messiah and mean that he was in just as much of a need of a savior from his sins as everyone else. It would have given his critics for once a legitimate reason to stone him and they wouldn't have needed to find false witnesses at his trial, but they didn't even seem to notice that he made such a radical statement. Doing away with the commands of God would have been a major doctrinal issue, not something relegated to a parenthetical side statement.
Do you hold the view that the law was only given to Jews and not to Gentiles? If so, then that is inconsistent with the view that Messiah came to free Gentiles from the law because he didn't need to come to free them from something that they were never given in the first place. Having no more need for a teacher is not the same as having no more need to follow what they taught you. When someone graduates from first grade to second grade, they come under a new teacher, but does the teacher tell them to forget everything they learned in first grade so that they can start fresh or does the teacher build upon what they were previously taught? The Spirit has the role of leading us in obedience to God's law (Ezekiel 36:26-27), so we have a superior teacher who can give us a superior understanding of how to do what is holy, righteous, and good, but that is still in accordance with God's law. In addition, the only way for there to be a superior way of doing what is holy, righteous, and good is if there is a superior God because God's instructions for how to do so are based on His holiness, righteousness, and goodness.