Well, obviously the connection between sul'dam and damane is known, since the sul'dam are the only ones capable of using the a'dam to control the damane. However since the sul'dam never actually start channeling on their own, it is likely that no one fully realised what the connection TRULY was.

I mean the Seanchan know that after 25 years, no one sparks. And the sul'dam are tested until that age so everyone "knows" that they cannot channel. And ofcourse even if a sul'dam was tested afterwards and caught, everyone would just say that she had managed to somehow avoid/cheat the test originally. This is twice as true since people would not want their precious system to be threatened.

I think it would take dozens and dozens of sul'dam being collared everywhere for the people to wake up and start wondering if maybe there was something strange here.



Yep, if it happened, it did so very rarely. And in those rare cases the implications could be dismissed as coincidence or accident or whatever.



Yeah, no sparkers in Seanchan have children. Or atleast its rare. There are probably some men and women who have children before they spark and are captured/killed. Still, you are right that to some extent the ability to channel and the spark(if it is inherited) has been culled in Seanchan.