I would like to say that you err on Sunday as God's true Sabbath. The Sabbath is mentioned 60 times in the New Testament as to 7 to 8 times for the first day of the week, which none of the first day of the week is about worship. All 60 times on the seventh day is about worship. In Acts, the Jews and Greeks are mentioned worshiping on the seventh day Sabbath four or five times.
Did you know that various forms of the word "sin" are mentioned 1,129 times in the Bible, but forms of the word "godly" are only mentioned 32 times? So do we then conclude that we should be sinful instead of godly?
I know, you're saying, "Wait a minute! The context makes a difference!" And you are absolutely right. Thus your argument based on the number of references is worthless.
You claim that all sixty references to the Sabbath are about worship. (Actually, there are 52 references to Sabbath in the New Testament.) Not so. "At that time Jesus went through the grainfields on the Sabbath. And His disciples were hungry, and began to pluck heads of grain and to eat" (Matthew 12:1). This is a reference to time and not to an act of worship. One counter demonstrates the claim of "every" is false, therefore the argument is worthless.
You claim that all seven or eight references to the first day of the week are not about worship. (Actually, there are 8 references to the first day of the week in the New Testament.) The partaking of the Lord's Supper is an act of worship. "Now on the first day of the week, when the disciples came together to break bread, Paul, ready to depart the next day, spoke to them and continued his message until midnight" (Acts 20:7). The giving of a contribution is an act of worship. "On the first day of the week let each one of you lay something aside, storing up as he may prosper, that there be no collections when I come" (I Corinthians 16:2). Thus, once again the claim of "every" is false, therefore the argument is worthless.
Yes, there are mentions of Greeks joining the Jews at their worship services. But that is before they became Christians.
"But when they departed from Perga, they came to Antioch in Pisidia, and went into the synagogue on the Sabbath day and sat down" (Acts 13:14).
"For those who dwell in Jerusalem, and their rulers, because they did not know Him, nor even the voices of the Prophets which are read every Sabbath, have fulfilled them in condemning Him" (Acts 13:27).
"So when the Jews went out of the synagogue, the Gentiles begged that these words might be preached to them the next Sabbath" (Acts 13:42). Though is a use of Sabbath as a time reference.
"On the next Sabbath almost the whole city came together to hear the word of God" (Acts 13:44). This is again a time reference.
"For Moses has had throughout many generations those who preach him in every city, being read in the synagogues every Sabbath" (Acts 15:21).
"And on the Sabbath day we went out of the city to the riverside, where prayer was customarily made; and we sat down and spoke to the women who met there" (Acts 16:13). The people worshiping here were not Christians, though Lydia shortly became one. The implication is that these women were following Jewish customs at this time.
"And he reasoned in the synagogue every Sabbath, and persuaded both Jews and Greeks" (Acts 18:4).
Thus what we find is that you are taking references to Jewish worship and claiming that Christians were doing the same without evidence.