Jesus began his ministry with the Gospel message to repent from our sins for the Kingdom of God is at hand (Matthew 4:17, 23), and the Mosaic Law was given to reveal what sin is, so it was how his audience knew what sin is, which means that repenting from our disobedience to the Mosaic Law and turning back to obedience is an integral part of the Gospel message. I would also agree with the article that the Gospel message should also include grace.
God has always be a God of grace and has always shown His grace to people throughout both the OT and NT. In Psalms 119:29, David asked God to be gracious to him by teaching him to obey His Law. In Genesis 6:8-9, it says that Noah found grace in the eyes of God and that he was a righteous man, and this was by no accident, but rather he was trained how to rightly live by grace and was righteous because he obeyed through faith. In Titus 2:11-14, it says that our salvation involves being trained by grace to do what is godly, righteous, and good, and to refrain from doing what is ungodly, and sinful, which is an accurate description of what the Mosaic Law was given to instruct how to do. According to Romans 1:5, we have received grace in order to bring about the obedience that faith requires. According to John 1:16-17, grace was added upon grace, so the grace of Christ was added upon the grace of the Law. According to Jude 1:4, ungodly people pervert God's grace into a license to sin, which is defined as the transgression of the Law (1 John 3:4). According to Strong's, "grace" is defined as "the divine influence upon the heart, and its reflection in the life", and when God's will is reflected in our lives, it takes the form of obedience to God's commands, so God shows His grace to use by training us how to walk in His ways in accordance with His Law.
We are not given the righteousness of Christ so that we will hide it under a bushel, but so that we will let it shine by following Christ's example of doing what is righteous in accordance with the Law. We are given the righteousness of Christ so that we become slaves of righteousness, not so that we will become free from following God's instructions for how to practice righteousness. The Law is God's instructions for how to practice righteousness, or in other words, for how those who are righteous ought to act, not for how to become righteous, so the Law was never given for the purpose providing the means of becoming saved in the first place, but as instructions for how we should act because we have been saved. So it is that much more true that we are not saved by obeying man-made works of law.
To fulfill the Law means "to cause God's will as made known in the Law to be obeyed as it should be" (2c), and this is precisely what Jesus proceeded to do six times throughout the rest of Matthew 5 after he said that he came to fulfill the Law. According to Galatians 5:14, everyone who has ever loved their neighbor has fulfilled the entire Law, which means that it is referring to obeying it as it should be, not to something unique that Jesus did. Likewise, in Galatians 6:2, bearing one another's burdens fulfills the Law of Christ, which doesn't refer to doing away with it, but to obeying it as it should be. In Romans 15:18-19, it says that Paul fulfilled the Gospel, which again doesn't refer to doing away with it, but to causing the Gentiles to become fully obedient to it in word and in deed. There are also many other examples speaking of people fulfilling the law in this manner found in other Jewish writings, so it has nothing to do with doing away with God's righteous standard.
In regard to Colossians 2:14, crosses were never uses as a means of disposing of laws, but rather what was written on crosses were the charges against the person being crucified or the violations of the law that they had committed (Matthew 27:37). This fits perfectly with our sins or violations of God's Law being nailed to Messiah's cross and with him dying in our place to pay the penalty for our sins, but does not fit at all with God doing away with His righteous standard. If Gentiles have never been under God's Law, then they have never needed Christ to give himself to redeem them from all Lawlessness.
According to John 5:46, Jesus said that Moses wrote about him, according to Luke 24:27, Jesus began with Moses and the Prophets interpreting to them all the things in Scripture concerning himself, according to Hebrews 10:7, the volume of the scroll is written about Jesus, and according to Romans 10:4, the goal of the Law is a relationship with Christ for righteousness for everyone who has faith, so the Law brings us to Christ because it is all about him and how to have a relationship with Him. Jesus set a perfect example for his followers to follow of how to walk in obedience to the Law, and we are told to follow his example (1 Peter 2:21-22), to walk in the same way he walked (1 John 2:6), and to be imitators of him (1 Corinthians 11:1), so the Law teaches us how to be like him, and our sanctification is about being made to be more like him.
Again, Jesus summarized the Law as being God's instructions for how to love Him and our neighbor, so there is nothing brand new about the command to love one another or distinct from what the OT commands. However, if you think Jesus added a brand new command, then you should think that he sinned in violation of Deuteronomy 4:2, and therefore could not be our Savior. Again, God did not make us righteous so that we would be free from following His commands for how to do what is righteous, but just the opposite. Hebrews does not say that God found fault with His righteous standard, but that he found fault with the people for breaking their covenant because of the hardness of their hearts, so the solution to the problem is not to do away with God's righteous standard, but to do away with what is hindering us from meeting it, so the New Covenant involves God taking away our hearts of stone, giving us hearts of flesh, and sending His Spirit to cause us to obey His Law (Ezekiel 36:26-27). The Spirit is not in disagreement with the Father about what conduct we should have and will not lead us to disobey any of His commands.
It is deeply inconsistent for you to hold the position that we are free from sin while holding the position that we are free to do what God has revealed to be sin in His Law. Rather, we have been set free from sin so that we might be free to live in obedience to God's Law and meet is righteous requirement (Romans 8:3-4). It is those who have a carnal mind who refuse to submit to God's Law in contrast with those who are walking in the Spirit (Romans 8:4-7).
The distinction between the letter of the law and the spirit of the law is reflected in modern discussions about law enforcement and is not in regard to whether the law should be obeyed, but in the manner in which people obey the law with respect to its intention. For example:
Leviticus 19:12 You shall not swear by my name falsely, and so profane the name of your God: I am the LORD.
Someone who is focused on obeying the spirit of the law will understand this as commanding us not to swear falsely, but someone who is focused on obeying the letter of the law will understand this as saying that we are free to swear falsely just as long as we don't do so in God's name. However, someone who was outwardly obeying this law in the correct manner might still not be obeying it according to its intention of teaching us how to walk in God ways in accordance with His attributes: holiness, righteousness, goodness (Romans 7:12), justice, mercy, faith (Matthew 23:23), love, joy, peace, patience, kindness, gentleness, and self control (Exodus 34:6-7, Galatians 5:22-23). Obedience to God has always been about growing in a relationship with Him based on faith and love and God has always disdained it when His people outwardly obeyed Him while their hearts were far from him, because that would be missing the whole point of God's commands. Paul counted obedience to the Law without being focused on growing in a relationship with Christ to be rubbish because again he was missing the whole point (Philippians 3:8).
It is again deeply inconsistent to say that because we are free from sin and have the Holy Spirit we can now produce holy fruit in our lives while saying that we are free from having to follow God's instructions for how to refrain from sin and for how to product holy fruit. While everything listed in Galatians 5:22-23 is in accordance with what the Law instructs, everything listed in Galatians 5:19-21 is against what the Law instructs, so again it is deeply inconsistent to say that we are free from the works of the flesh while saying that we are free from having to obey the Law that instructs against the works of the flesh. Dead works are the works that lead to death, which are sins in transgression of the Law, not obedience to what our God has commanded, which brings life. In John 14:23-24, Jesus said that if we love him, then we will obey His teachings, and that his teachings are not his own, but that of the Father who sent him, so he did not depart in the slightest from what the Father had commanded, which is the good way where we will find rest for our souls (Matthew 11:28-30, Jeremiah 6:16-19).