So it appears that we agree that the apostles and disciples did get together to observe the Sabbath on Saturdays.
What you don't acknowledge is that they then got together on Sundays to observe the new Christianity because Christ rose from the dead on a Sunday -- the third day after his death on the Cross.
And as your statement in post #2154, this one is equally false. Our Lord resurrected "Late on Sabbath" [Matthew 28:1]. The false doctrine you are trumpeting is easily dismissed by a casual read of scripture.
Jesus wasn't resurrected on Sunday, btw. And even if He had been, it is still not justification from breaking one of God's commandments.