Rand,
These are very nice swords. AssadAllah and Shah Abbas stamps are typical combination indicating a maker (most probably a School) and a ruling principal. The pitting on a crossguard is a nice indication of it's age
As for the line at the ridge of the blade: Yes, many wootz shamshirs have it!!!!! It indicates a last
fold when the sword was made. My personal guess is that the maker's intention was to show that the blade was indeed folded (as to proove the process). I can see them saying to the buyer: "Look, it was folded 1000 times, and this is the last fold line"

Just like modern dealers say: "Look, it is hand made". An inlay could have been added for decoration purposes, and/or to protect the opening from dust, debree... and blood

Again, purely my guess.
Very nice collection. Do these swords have any scabbards?