Well....evidently difficult for you as all of your sources except one date from after the first century. And there is no proof of the authenticity of the other.
The Didache says.....according to your thread: But every Lord's day . . . gather yourselves together and break bread, and give thanksgiving after having confessed your transgressions, that your sacrifice may be pure.
Just what does the original Language here call the "Lord's Day"? Was this canonized? Why not? Oh....they found it much later? I see.
The Didache also says that day is “the day of the sun”.
The fact is, Saturday evening gatherings are what is spoken of in the Didache. This is what Acts 20:7 clearly references. In the Scriptures, the day ALWAYS begins at sunset.