Line 5 - By the talents of Abrahams kin can the key to the greatest of treasures of which nothing now on this earth can prove of better fortune nor be its equal could be found.

Abraham's kin would be the descendants, or the inheritors, of the Silver Cup of Benjamin. There is a theory that some of the tribes of Israel fled the land and migrated to many places all over. One of these theories is that the tribe of Benjamin, among other tribes, managed to migrate and settle into Europe. Although interesting, there is too much speculation out there on the subject, and I don't want to get caught up in a lengthy discussion about here.

This would also seem to reference the warning/intro page about "Abraham the Jew" and the "Nation of the Jews" "Dispersed Among the Gauls". This also alludes to the idea that the descendants of Abraham (albeit it could be a different Abraham being described as "the Jew") passed into Europe, as the ancient land of Gaul was placed there.

In any regard, it is clear that with the name of "Abraham" (which means "father to many"), those who are being referred to as his descendants would be his "followers".

"the greatest of treasures of which nothing now on this earth can prove of better fortune nor be its equal could be found."

This is of course a reference to Abbe Fouquet's letter to his brother Nicholas Fouquet, Superintendent to King Louis XIV of France, after a meeting with Poussin in Rome.  In it he states:  "He and I discussed certain things, which I shall with ease be able to explain to you in detail - things which will give you, through Monsieur Poussin, advantages which even kings would have great pains to draw from him, and which, according to him, it is possible that nobody else will ever rediscover in the centuries to come. And what is more, these are things so difficult to discover that nothing now on this earth can prove of better fortune nor be their equal."

What can't prove of better fortune nor be their equal is this treasure.  The key  to it can be found by the descendants, or followers, of Abraham.  

For me, this is a spiritual treasure.  It has to do with the ascension described in the earlier lines, but also has to do with conquering the serpent Apep (Apophis) in order to do so.  I complete (or destroy) this guardian demon at Noon.  Noon is straight up.  The demon would be the serpent Apophis.