Exo 31:16 Wherefore the children of Israel shall keep the sabbath, to observe the sabbath throughout their generations, for a perpetual covenant.
Exo 31:17 It is a sign between me and the children of Israel for ever: for in six days the LORD made heaven and earth, and on the seventh day he rested, and was refreshed.
This seems pretty clear. It is a sign between the Lord and the children of Israel...FOR EVER. It is a PERPETUAL covenant. The seventh day, the sabbath of the Lord.
The Lord of the Sabbath had the prerogative to change the day of the week that was the Sabbath from the last day to the first. This He did but rising from the dead on the first day of the week, gathering with His disciples after the resurrection on the first day of the week, and His apostles meeting with the flock, breaking bread, and hearing their teaching on the first day of the week.
You're got the traditional explanation down pat. However, nowhere in scripture is the 7th day sabbath changed to any other day. The 7th day was never made unholy or desanctified by anyone, much less Jesus.
Historically, the sabbath was changed by the early Roman church for a variety of reasons. The Roman church changed it on its own authority. They believe that they are the true church of God and have the authority to change it. Protestant churches apparently go along with this notion because it has become entrenched in history and tradition. I would recommend that you study the issue.
Historically, if you include the NT. You have yet to show us all a place in the NT where the early church post resurrection met on the last day of the week.