interesting. But do you mean the movement reported by Paul as containing James and Peter as members, or do you mean the community of Paul's followers, to whom he wrote his letters? For the two don't appear to have been the same, as evidenced by Galatians 2, and other places in Paul's writings. Or if they were at first the same, there was an early split, not merely between the DSS sect and the Jesus people, as you state, but between the James people and Paul, within the Jesus group.
I'm not really being that specific about details of any named individuals such as anyone called James or Peter etc. Even in the case of the canonical gospels where such names are frequently mentioned, it always seems to me shaky in the extreme to think that we should take mention of such names at face value as if the stories of those supposed individuals were actually true or in any way reliable.
Imho, documents such as the gospels are nowhere near being reliable enough to even consider taking the mention of such named individuals seriously, and trying to make deductions from whatever is said about (say) someone called “James” doing various things. I would disregard all that entirely.
Afaik, the DSS do not mention any of those named individuals. So I don’t think that issue of what to believe about James or Peter, even arises in reading the DSS. There might be coded reference there to specific individuals (whatever their actual names), but that would be heaping more & more guesswork on top of other guesswork.
So all I’m saying about the importance of the DSS is that, what the scrolls do appear to show is that 100 years or so before the time of St. Paul and Jesus, Jewish religious beliefs and practices in that region were already concentrating on belief in a messiah who was thought to be in some sense a supernatural figure rather than a human leader in the line of King David, and who’s role was to gather around him the faithful righteous followers of the scripture in order to lead them safely into heaven on what was to be an imminent day of judgement.
To that extent, the basis of the beliefs set out in the DSS, appears to be very similar to that which was preached around 50AD by Paul. And the whole thing was also similar to what appeared much later (say from around 100AD onwards) in the first examples of the gospels.
IOW – there seem to be very obvious similarities between the DSS community and the emergence of Christianity as described first by Paul, and then as later elaborated and extended in the gospels.
Without going into detail – in the Letters of Paul for example, there are various phrases and wordings which, prior to discovery of the DSS, were assumed to be simply the unique language of Paul. However, after the discovery of the DSS, which is of course relatively very recent in terms of biblical Christian history, it’s now clear (afaik) that a number of the phrases in Pauls letters are in fact almost word-for-word repetition of identical phrases in the scrolls.
Various later Christian practices as described in the gospels can of course also be found as similar parallels in the DSS, eg the notion of a “last supper”. The examples are not always literally identical, and we should not expect them to be 100% the same, but the basic ideas and practices are clearly similar across the whole of that period from the earliest DSS circa. 170BC, through to the latest dates of the canonical gospels around say 200AD.
Overall, all of these religious practices and beliefs, whether from the DSS or from 100 to 300 years later with Paul’s letters and the gospels of Mathew, Mark, Luke and John, are (afaik) simply elaborations of what was believed to be the religiously correct interpretation of the coded prophecies given in the various books of the Jewish OT dating back to at least 500BC.
So, IOW - between the prophecies of the ancient Jewish OT, and the extensive description of Jewish beliefs in the DSS, it seems to me quite clear where the later religious ideas of Christianity had arisen.
