On Korriban, a sith says that over time, Sith blood was diluted by that of their slaves until now outward signs like red skin are rare. In a FP, we're also told that 99% of the people in the empire carry some sith blood. Sith and other species can definitely reproduce.
Yes, you are right, of course. That would be
And of course there is this FP. So I guess the matter is settled and as the SW story goes, the way it implies certain facts, the most canon races are Pureblood and Human. Pureblood is probably the most story compatible option, while the Human is the second best, almost as good as Pureblood. If a Pureblood like Exal Kressh (i.e. a Pureblood who looks like her, almost Human) had offspring with a Human Sith Lord and that offspring would have his/her own offspring also with a Human Sith Lord, the heir to their bloodline could very well be Human SW who could then