Welcome! Kick off your shoes and sit a spell! The issue here is what did God command? You should that according to Socrates Scholasticus and other church historians, the Sabbath was kept for many many centuries by the Christian church...until...another "Church" took control of the region, and Sabbath was done away with and Sunday was set up.
And who or what is this Socrates Schasticus that we should just believe him.
Specifically, Paul said, "lay by him in store", not in a Sunday morning collection plate. Where did people "store" things "by them"? At home. Honest scholars agree Paul told the people to lay something aside at home for Paul so that when he swept into town, he could scoop up the money and make haste to the suffering church in Jerusalem instead having to wait for people to run to the bank or find a buyer for their goat or whatever.
1 Corinthians 16:2
Upon the first day of the week let every one of you lay by him in store, as God hath prospered him, that there be no gatherings when I come.
So according to you, they met on saturday, took money and set it aside at home. Then when Paul came- you seem to think he went house to house to collect what people lay in store.
People met in houses in these days and the fact that Paul said to lay by in store so there would be no collection when He came, showed they set this money aside (most likely with the local elder) on sunday.
Also Sabbath keeping is not for worship or communal gatherings. The Sabbath as God commanded was that it was to be a day of rest!
Here is the entire extent of the3 command of the Sabbath:
8 Remember the sabbath day, to keep it holy.
9 Six days shalt thou labour, and do all thy work:
10 But the seventh day is the sabbath of the Lord thy God: in it thou shalt not do any work, thou, nor thy son, nor thy daughter, thy manservant, nor thy maidservant, nor thy cattle, nor thy stranger that is within thy gates:
11 For in six days the Lord made heaven and earth, the sea, and all that in them is, and rested the seventh day: wherefore the Lord blessed the sabbath day, and hallowed it.
also, God made it very clear that the Sabbath was a covenant between Him and the Jewish people as a perpetual covenant.
Exodus 31:
13 Speak thou also unto the children of Israel, saying, Verily my sabbaths ye shall keep: for it is a sign between me and you throughout your generations; that ye may know that I am the Lord that doth sanctify you.
14 Ye shall keep the sabbath therefore; for it is holy unto you: every one that defileth it shall surely be put to death: for whosoever doeth any work therein, that soul shall be cut off from among his people.
15 Six days may work be done; but in the seventh is the sabbath of rest, holy to the Lord: whosoever doeth any work in the sabbath day, he shall surely be put to death.
16 Wherefore the children of Israel shall keep the sabbath, to observe the sabbath throughout their generations, for a perpetual covenant.
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.