'It is unlikely that Christ would hold them responsible for the blood shed of a fictional person by another fictional person. The crimes of persecution from Abel's murder to Zachariah's murder, must be counted by Jesus as history.'
This is to fail entirely to get the point. The point is that the opposition of the Pharisees to righteous people in one age will earn them condemnation and punishment for opposition to them in any age, in every age. Jesus mentioned the names of Abel, Zechariah and all the opposed prophets of Israel, to emphasise that the Pharisees were in diametric opposition to their own claimed culture and faith. That's an uncomfortable if unremarked lesson for many today, of course. Seeing a literal interpretation of Abel in this passage is quite
beside that point.