God gave that covenant to the Hebrews, who were his people, whom he had freed from slavery. They were to show themselves to be his people by being holy - or set apart - and live holy lives. That meant worshipping him as the only God, not having anything to do with idols, following his rules for right living and offering sacrifices when they sinned, not touching unclean people who were bleeding or had skin complaints or dead people, not eating unclean foods, wearing clothes of pure cotton, not mixed fabrics, and keeping themselves pure by marrying only other Hebrews; no one from outside their faith. That is how they were to live in gratitude to a holy God who had called them and made them holy.
Is God still holy today? Of course. Does he have people he has called to be his own? Of course - all those who believe that he sent his Son to be the spotless Lamb of God who takes away the sin of the world; all those who believe that, through him, they have been freed from the slavery of sin and death. Has he commanded us to live in such a way so as to reflect his light, his glory and our relationship with him? Of course. But the latter does not include going back to the OT laws and putting ourselves under them, or in bondage to them. It may be very good to follow the dietary laws, but it's not a command for us.
1 Peter 1:14-16 As obedient children, do not be conformed to the passions of your former ignorance, 15 but as he who called you is holy, you also be holy in all your conduct, 16 since it is written, “You shall be holy, for I am holy.”
What did it mean to an Israelite to have a holy conduct? What did it mean to the author of 1 Peter to have a holy conduct? If the answer to those questions is different, then why did verse 16 quote from the OT where it talks about keeping dietary laws? How can we have a holy conduct while at the same time disregarding God's holy instructions for how to do that? It is just as important for Gentiles to have a holy and righteous conduct as it is for Jews, so I see no good reason for why you say God's laws are excluded. We can not reflect His light if we refuse to do His will.
God's laws define what sin is as we are not permitted to sin, so we should not ignore them. It is not God's laws that put us in bondage, but rather it is sin in violation of God's laws that put us in bondage. We have been set free from sin so that we can be free to become slaves of obedience, leading to righteousness, and slaves of righteousness, leading to sanctification (Romans 6:15-19). True freedom is the freedom to do what is righteous in accordance with God's righteous laws.
Jesus gave us lots of commands, teaching and instruction on how to live - following strict food laws that were not given to Gentiles was not part of that.
John 7:16 "My teaching is not My own," Jesus replied. "It comes from Him who sent Me.
Jesus didn't teach anything different from what the Father had commanded and Gentiles were never exempted for having to obey the Father. It is only by faith that we can uphold God's law (Romans 3:31) and receive it as they were intended, as a divine privilege and a delight, as the Psalmists understood (Psalms 1:2, Psalms 119) and as Paul understood (Romans 7:22).
And the statement in Mark makes it clear that by saying this, Jesus declared all foods to be clean. Nowhere did Jesus insist that all Gentiles follow Jewish dietary laws after they believed in him.
Mark 7:19 Because it doesn’t go into his heart but into his stomach, and then into the sewer, thereby expelling all foods.” (ISV)
Mark 7:19 because it doth not enter into his heart, but into the belly, and into the drain it doth go out, purifying all the meats.' (YLT)
There is some debate over how Mark 7:19 should be translated, but it should be noted that there is no "and thus he declared" in the Greek. I think the ISV expresses the idea behind the verse the clearest because the topic is about kosher food that is eaten with unwashed hands becoming common or defiled and then making the person who eats it common or defiled. So Jesus was talking about the digestive process of how such food is eaten and expelled from the body without entering the heart to show that their man-made ritual purity law was insignificant and that their concern for ritual purity was out of balance with their concern for moral purity. As I said, Matthew 15:20 makes it clear that he never switched topics from man-made ritual purity laws to God's dietary laws.
Furthermore, just had just finished lambasting the Pharisees for being hypocrites for setting aside the commands of God to follow their own traditions, so if Jesus had set aside the commands of God just a few verse later, then that would have made him an even bigger hypocrite. On top of that, the Bible warns against anyone who performed signs and wonders, but taught them not to follow God's commands (Deuteronomy 13:4-6), so if Jesus had done that, then he would have disqualified himself as the Messiah and for once given his critics a legitimate reason to try to stone him. They wouldn't have needed to find false witnesses at his trial, but no one even mentioned this incident at his trial. It would have caused an uproar, but not one even seemed to have noticed. This would have been a major doctrinal issue, not something relegated to an aside comment in a discussion that wasn't even about dietary laws.
The early church did not stop being Jews after they witnessed the resurrection and received the Spirit at Pentecost, so if they DID observe all the food laws (there is no Scripture to say this) it may have been because it took a while to understand what their new faith meant.
I've seen estimates that Peter's vision was between 7-17 years after Christ's ascension, so up until that point God's assembly was entirely comprised of either Jews or Jewish proselytes. Paul and James took steps in Acts 21 to show that they had not teaching Jews to forsake God's law and Paul claimed that he believed everything laid down by the Law and written in the Prophets, so if they weren't teaching that, then who was? Our faith in the Messiah does not mean that we can forsake his laws, but just the opposite, so it was not those Jews who did not understand what they faith meant, but rather it's you. It is the carnal mind that does not submit to God's laws (Romans 8:7).
They met on the first day of the week, for example, to break bread.
The Sabbath lasted from sundown on Friday evening to sundown on Saturday evening and the first interval between Sabbaths was the Havdalah service immediately following the Sabbath on Saturday evening. This practice was nothing new or out of the ordinary. Paul had been preaching from evening to midnight, not all day, and was leaving on what we'd call Sunday to travel. Even if they had gathered to eat together on what we would call Sunday, that wouldn't mean anything special because they had the freedom to eat together on any day of the week. They still continued to keep the Sabbath all throughout Acts.
At the council of Jerusalem, James sent a letter to Gentile believers telling them to abstain from blood, (not pork) and from meat offered to idols. Yet only a few years later, Paul, who took this letter to the Gentiles, told them that eating meat offered to idols did not make them unclean, that an idol was nothing and that the kingdom of God is not a matter of food and drink. This is a former Pharisee talking.
If you hold hard that those four laws were an exhaustive list of every of everything that would be required of Gentiles, then that would exclude the teachings of Jesus and other laws commanded in the NT. On the other hand, if you say that other laws were obviously included, then I'd agree with you. The kingdom of God is not a matter of food and drink insofar as the context is about disputable matters of opinion (Romans 14:1) rather than the commands of God. Man's opinion about what is food must yield to what God has given to be eaten as food, so God's dietary laws weren't even being discussed in Romans 14.
1 Corinthians 10:21-22 You cannot drink the cup of the Lord and the cup of demons. You cannot partake of the table of the Lord and the table of demons. 22 Shall we provoke the Lord to jealousy? Are we stronger than he?
But we don't have a commandment to keep them - not the food and hygiene laws anyway.
More accurately, Gentiles don't have a commandment not to keep them. It should be relatively straightforward that if you join a religion, then you follow its laws. It should be relatively straightforward that if you're told not to sin and the Bible says eating unclean animals is a sin, then you are not to eat unclean animals. It should be relatively straightforward that if we are followers of Christ, then we should follow his example of obedience. WWJD? He'd obey God's Torah and make disciples to teach them to do the same.