how is the Master able to give Eichorst or Kelly or any strigoi

The Master has some sort of "leash" or overarching control over each of his progeny. From what I understand, if he releases enough of his will or "loosens his leash" enough on a chosen strigoi, they are then able to access old memories and pieces of themselves to be able to speak and move fluently. As Eichhorst explains it, it takes awhile to get used to controlling the contractions and being able to move fluently. But after some experience it all becomes second nature.

I don't know about the whole makeup thing, I think we just have to accept that Eichorst is crazy good with concealer.
As for the free will, I don't think that they have any, not in the real sense anyway. I think they have been promoted from mindless drones to soulless animals with intellect. So they have their brains' back, but none of what makes them human. No capacity for love etc. just affection and other biological feelings. Obviously, not all biological feelings though, because, you know...