The OT personalities acted out things that we can look back upon and analyze as types and shadows of things to come or things which have already come. Much like a teenager passes through puberty is like crossing a threshold and the same with a making a marriage bond, the very rites of passage aren't necessarily diminished because they have a higher meaning associated with them.

As for Melchizedek, there are quite a few who have made a link between Melchizedek and Krishna. Of course, there are those who point to Shem.

Abraham having been called out was clearly learning more richly what and who he had become. The Sarah and Hagar paradigm is still carried on in the prohibition of saints marrying non-believers. Allegorical does not make something fictional.