To begin where the last post ended— In none of this literature is Adam ‘everyman’, any more than Eve is ‘every woman’ though there are some hints in the latter direction in Sirach.
What is in any case assumed in all these intertestamental reflections is that Genesis is telling a historical story about real people who affected not only themselves but their descendants in various ways. They are not merely literary figures who set bad examples for those who read their stories. It is thus not helpful to say “no author cared about giving Adam a historical reading” (p. 168). None of these authors defended the historicity of Adam because it was not a question or an issue, nor did any of them view the historical Adam in light of later Christian tradition. This is however very different from saying none of them thought Adam was a historical= real person in space and time. In fact, none of them would have spoken of Adam as they do in regard to genealogies and effects on descendants if they did not take it for granted that he and Eve were real persons. And finally, at Qumran the story is the same. CD 10.8; 4Q504; 4 Q167 1 QS 3-4 depict an Adam who is the first breaker of faith with God, the first breaker of the covenant, the first formed in, and the first to deform the image of God, and so on.
Yes, the later full form of the Christian analysis of Adam by Augustine and subsequent interpreters is not found in these texts, and doubtless some of those interpreters went not just beyond but against what the Bible says, and need correction. This however doesn’t mean that anyone in the Biblical and intertestamental tradition thought Adam and Eve were mere literary figures, or ciphers for everyone, but not real ancestors of God’s people.