That revelation was apparently set at the very first council in 50 AD,
Gentiles do not need to convert to the Laws of Judaism, it's a fact that it was illegal for Christians to go to church on the Sabbath and even Sunday they had to sneak out to a friends house and worship before dawn and then again at night because it was also illegal just to be a Christian in general.
I don't think you are too familiar with the history of the 1rst 2nd and 3rd Century churches or you would know this.
Christians used Sunday especially after the Temple was destroyed, they were treated pretty badly as well, but full of the Holy Spirit, so your argument that they are unsaved martyrs because they didn't go to church on Saturday is rather absurd and challenged.
All the early church came together on the Sabbath, Jewish or Gentiles and it was that way till apostasy got into the church.
https://www.sabbathtruth.com/sabbath-history/sabbath-through-the-centuries
Here is from a sermon I came across by Timothy Lee Arnett. I searched but cant find it anymore, but have it in my notes.
"When Jesus customarily went into the synagogue on the Sabbath day, he didn't go as a Jew, on behalf of the Jewish nation, but as the Son of man, as the second Adam, representing the entire race to God.
Luke 4:14-21 King James Version (KJV)
14 And Jesus returned in the power of the Spirit into Galilee: and there went out a fame of him through all the region round about.
15 And he taught in their synagogues, being glorified of all.
16 And he came to Nazareth, where he had been brought up: and, as his custom was, he went into the synagogue on the sabbath day, and stood up for to read.
17 And there was delivered unto him the book of the prophet Esaias. And when he had opened the book, he found the place where it was written,
18 The Spirit of the Lord is upon me, because he hath anointed me to preach the gospel to the poor; he hath sent me to heal the brokenhearted, to preach deliverance to the captives, and recovering of sight to the blind, to set at liberty them that are bruised,
19 To preach the acceptable year of the Lord.
20 And he closed the book, and he gave it again to the minister, and sat down. And the eyes of all them that were in the synagogue were fastened on him.
21 And he began to say unto them, This day is this scripture fulfilled in your ears.
This particular Sabbath Day, Jesus declared Himself to be, the long awaited for Messiah to Israel according to the prophecies in Isaiah. But the prophecies also show that He would give the light to the Gentiles as well. We see that the verses in Acts 13:42-44 confirm the truth, that Gentiles after their conversion to Christ, kept the Sabbath.
Acts 13:42-44 King James Version (KJV)
42 And when the Jews were gone out of the synagogue, the Gentiles besought that these words might be preached to them the next sabbath.
43 Now when the congregation was broken up, many of the Jews and religious proselytes followed Paul and Barnabas: who, speaking to them, persuaded them to continue in the grace of God.
44 And the next sabbath day came almost the whole city together to hear the word of God.
But many take for granted the surrounding verses referenced from the prophecies of Isaiah to show that it was foretold of the Gentiles worshiping on the Sabbath after Messiah had brought His Salvation. This event was in fulfillment of many Old Testament prophecies, for example:
Isaiah 49:6-9 King James Version (KJV)
6 And he said, It is a light thing that thou shouldest be my servant to raise up the tribes of Jacob, and to restore the preserved of Israel: I will also give thee for a light to the Gentiles, that thou mayest be my salvation unto the end of the earth.
7 Thus saith the Lord, the Redeemer of Israel, and his Holy One, to him whom man despiseth, to him whom the nation abhorreth, to a servant of rulers, Kings shall see and arise, princes also shall worship, because of the Lord that is faithful, and the Holy One of Israel, and he shall choose thee.
8 Thus saith the Lord, In an acceptable time have I heard thee, and in a day of salvation have I helped thee: and I will preserve thee, and give thee for a covenant of the people, to establish the earth, to cause to inherit the desolate heritages;
9 That thou mayest say to the prisoners, Go forth; to them that are in darkness, Shew yourselves. They shall feed in the ways, and their pastures shall be in all high places.
