Sometimes an answer will make multiple questions irrelevant, that's what's going on here.
It floats very well and there is ample Biblical evidence for assembling on Sunday.
Colossians 2, 16
Let no man therefore judge you in meat, or in drink, or in respect of an holyday, or of the new moon, or of the sabbath days: Which are a shadow of things to come; but the body is of Christ
There is no spinning out of the fact that the Feasts of Israel (the Feasts of the Lord) were weekly (the Sabbath's (notice the plural), the Monthly and the yearly. These feasts are detailed explicitly in the Old Testament (Leviticus 23
) and here in the New are re-classified as "SHADOWS" that point to what fulfilled them (Christ).
Romans 14, 5
demonstrates the same point that Colossians 2
does by showing that in the big picture there isn't anything more important about the Sabbath than Thursday. Seriously Icy, can you imagine a New Testament Scripture that told Christians that one man believes he can sleep with other men's wives and another man believes he can't and therefore let each man make up his own mind! This is another frank and stinging reality slap that the Sabbath is CEREMONIAL exactly as both the Old Testament and New Testament say it is.
The New Testament Scriptures never speak that way about moral AKA non-ceremonial laws - can you imagine God telling Christian converts from Paganism or even Jews who accepted Christ to let no one judge them for murder, stealing, adultery, murder and the like? This alone should demonstrate the Feasts of God were ceremonial and as such not obligatory for Christians exactly as the Scripture tells us is the case.
So, we start from a position that comes straight out of the Bible - that observing the Sabbath is of no significance . Observing the Sabbath has as much to do with Salvation as carrying a piece of fried chicken in your left shirt pocket does.
There is a New Testament command for Christians to assemble however.
Hebrews 10, 23-27
Let us draw near with a true heart in full assurance of faith, having our hearts sprinkled from an evil conscience, and our bodies washed with pure water. Let us hold fast the profession of our faith without wavering; (for he is faithful that promised And let us consider one another to provoke unto love and to good works: Not forsaking the assembling of ourselves together, as the manner of some is; but exhorting one another: and so much the more, as ye see the day approaching. For if we sin wilfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins, But a certain fearful looking for of judgment and fiery indignation, which shall devour the adversaries
This is CHRISTIAN ASSEMBLY
being spoken of here therefore going to the Temple or Synagogue on the Sabbath day would be violating the command in Hebrews 10 because Christians assembling with Jews ISN'T assembling "OF THEMSELVES TOGETHER
is extremely clear.
And they [ Apostles & other Christians ], 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,
The earliest Christians continued DAILY to assemble with their fellow Jews at the Temple (where actual sacrifices were still going on) AND at the Synagogues but came together AS CHRISTIANS on the 1st day of the week. Understand the difference between an assembly of Christians with Jews still practicing Judaism AND an assembly OF Christians.
Acts 20, 7
And upon the first day of the week, when the disciples came together to break bread, Paul preached unto them, ready to depart on the morrow; and continued his speech until midnight
The Scriptures state that the Apostles & converts to Christianity were continuing DAILY in the temple and also meeting at Synagogues yet it was on the 1st day of the week they had an assembly of THEMSELVES
together AS A CHURCH
. The same concept is spelled out clearly in 1 Corinthians 11, 18 - end of the chapter