The fact that Force-sensitive Chiss are mostly women might be a cultural rather than biological quirk, as the Chiss are mentioned to have Amazon Brigades of mercenaries. If the girls were raised with this in mind, it would lead to greater focus and emotional control, both of which would lend themselves well to manifesting the Force, while for boys this would be more of a random chance.
Since Force-sensitive Chiss children have the ability of precognition, Thrawn is well aware of the possibility of being able to see the future. When he defeats the Bendu in the season 3 finale of Star Wars Rebels, he almost anxiously asks the Bendu what he sees, and is left rightly apprehensive at the prediction of his fate.
The fact that Thrawn knows Vader's Secret Identity is really not surprising. Aside from the fact that Thrawn is a genius with access to vast amounts of information from which he could deduce the connection, there's one very obvious clue: Vader's lightsaber hilt is essentially a larger, darker variation of his Jedi weaponnote Particularly, it is nearly identical to his first lightsaber. Despite Thrawn meeting Anakin after he replaced it, the one he wields as Vader still bears a close resemblance to his second one as well. Considering Thrawn's Awesomeness by Analysis skills in terms of art, and Vader may as well have worn a sign proclaiming "I used to be Anakin Skywalker."
Why does Vader take Thrawn figuring out he used to be Anakin so badly? Because he's still reeling from his confrontation with Ahsoka months prior. It's repeatedly established that he does not want to be even obliquely reminded of who he once was, so Thrawn managing to figure out his identity just by interacting with him makes him angry.
It's also another sign that the persona of Vader is starting to crack, however slightly. Ahsoka made the first cut during their confrontation on Malachor, and now Thrawn has made the second. Eventually, those will add-up with the ones inflicted to Vader over the course of the Original Trilogy, paving the way for Luke to redeem his father.
