I wanted to answer this part of your remarks separate from that of the details I requested to rebut the link I shared, as you said there were multiple errors therein.
As pertains to Constantine and his council changing the day of worship to Sunday:
March 7th, 321 AD Codex Justinianus, lib. 3, tit. 12, 3
On the venerable Day of the Sun let the magistrates and people residing in cities rest, and let all workshops be closed. In the country, however, persons engaged in agriculture may freely and lawfully continue their pursuits; because it often happens that another day is not so suitable for grain-sowing or for vine-planting; lest by neglecting the proper moment for such operations the bounty of heaven should be lost. (Given the 7th day of March, Crispus and Constantine being consuls each of them for the second time
As pertains to Easter and Constantine.
On the Keeping of Easter. From the Letter of the Emperor to all those not present at the Council. (Found in Eusebius, Vita Const., Lib. iii., 18–20.) When the question relative to the sacred festival of Easter arose, it was universally thought that it would be convenient that all should keep the feast on one day; for what could be more beautiful and more desirable, than to see this festival, through which we receive the hope of immortality, celebrated by all with one accord, and in the same manner? It was declared to be particularly unworthy for this, the holiest of all festivals, to follow the custom [the calculation] of the Jews, who had soiled their hands with the most fearful of crimes, and whose minds were blinded. In rejecting their custom,113 we may transmit to our descendants the legitimate mode of celebrating Easter, which we have observed from the time of the Saviour’s Passion to the present day [according 113 We must read !"#$%, not &"'#$%, as the Mayence impression of the edition of Valerius has it. 114 NPNF (V2-14) Philip Schaff to the day of the week]. We ought not, therefore, to have anything in common with the Jews, for the Saviour has shown us another way; our worship follows a more legitimate and more convenient course (the order of the days of the week); and consequently, in unanimously adopting this mode, we desire, dearest brethren, to separate ourselves from the detestable company of the Jews, for it is truly shameful for us to hear them boast that without their direction we could not keep this feast.
As pertains to Constantine and his council changing the day of worship to Sunday:
March 7th, 321 AD Codex Justinianus, lib. 3, tit. 12, 3
On the venerable Day of the Sun let the magistrates and people residing in cities rest, and let all workshops be closed. In the country, however, persons engaged in agriculture may freely and lawfully continue their pursuits; because it often happens that another day is not so suitable for grain-sowing or for vine-planting; lest by neglecting the proper moment for such operations the bounty of heaven should be lost. (Given the 7th day of March, Crispus and Constantine being consuls each of them for the second time
As pertains to Easter and Constantine.
On the Keeping of Easter. From the Letter of the Emperor to all those not present at the Council. (Found in Eusebius, Vita Const., Lib. iii., 18–20.) When the question relative to the sacred festival of Easter arose, it was universally thought that it would be convenient that all should keep the feast on one day; for what could be more beautiful and more desirable, than to see this festival, through which we receive the hope of immortality, celebrated by all with one accord, and in the same manner? It was declared to be particularly unworthy for this, the holiest of all festivals, to follow the custom [the calculation] of the Jews, who had soiled their hands with the most fearful of crimes, and whose minds were blinded. In rejecting their custom,113 we may transmit to our descendants the legitimate mode of celebrating Easter, which we have observed from the time of the Saviour’s Passion to the present day [according 113 We must read !"#$%, not &"'#$%, as the Mayence impression of the edition of Valerius has it. 114 NPNF (V2-14) Philip Schaff to the day of the week]. We ought not, therefore, to have anything in common with the Jews, for the Saviour has shown us another way; our worship follows a more legitimate and more convenient course (the order of the days of the week); and consequently, in unanimously adopting this mode, we desire, dearest brethren, to separate ourselves from the detestable company of the Jews, for it is truly shameful for us to hear them boast that without their direction we could not keep this feast.
The apostles already worshipped on sundays for 300 years prior to this.
So to say that Constantine changed it is wrong.
Constantine just made it universal for Romans, apparently.
Not really sure why you posted about easter. Except to show that Constantine was a Christian. Good for him.