You inserted the stuff in the brackets.
From the link: Wherefore, also, we keep the eighth day with joyfulness, the day also on which Jesus rose again from the dead.1670
This plainly says they kept both the Sabbath and their 8th day. If only they had a whole Bible like we do today...
What Bible are you using?
The 'also' is in the wrong place for that assertion. It says "Wherefore, also, we keep the eighth day." You make it say "we also keep the eighth day." It does not say they did both.
If only they had a whole Bible like we do today...
You only have one because a canon was crystallized by those apostate Sunday-keepers. It must therefore be interpreted through the lens of those who selected the contents of the canon.
You are misreading Barnabas and reinterpreting his words apart from the historical setting.
Jesus rose on the first day of the week, which Barnabas also refers to as "the eigth day". Only historical revisionists will find the ECF teaching that Jesus rose from the dead on the last day of the week. He did not. He rose on the first day, and the church universal has always recognized this fact by establishing Christian worship on the first day according to the tradition of the apostles as recorded in Scripture.