I'm confused. You had 5 reviewers for an abstract and one of them produced 7 pages of criticism? I'm aware of many venues in Chem that are abstract submission, but it sounds like you were in a full-paper situation.
OP never said it was an abstract - they are from chem/bio (like me), where papers are submitted primarily to journals, not conferences. They mentioned abstracts in response to your comment about writing to the "steering committee of the conference"