You are forgetting that there were no Christian churches at that time... where else was Paul and the others to preach? Yes, they were to take the Gospel to the Jews first but after the stoning of Stephen, the Jews as a nation came to the end of their probationary time as detailed in Daniel 9:24.
Have you asked yourself why, after the apostles were done teaching the Jews in the synagogue on Sabbath, that they didn't teach the gentiles the next day, the 1st day? If the contention of 1st day worship is to be believed, why don't we see these things in the Bible? The apostles are always recorded as teaching on the Sabbath, both to Jews and Gentiles. There is no evidence of the apostles breaking the Commandment to keep the Sabbath Holy.
Btw, breaking bread on the 1st day does not convey worship or holiness. Acts 2:46 shows this premise to be false.
Acts 2:46
And they, continuing daily with one accord in the temple, and breaking bread from house to house, did eat their meat with gladness and singleness of heart,