It basically boils down to "What does Kushinada gain by pointing Jenazad at Miu?" On the surface, the answer is "nothing." Kushinada doesn't seem to have any particular loyalty or affection to Jenazad (or any of the others save perhaps the One Shadow). But if you look deeper, Jenazad interfering with Miu could set up a chain of events that gets Jenazad, who has been presented as one of the most skilled/powerful of the Nine Fists (along with Kushinada) "taken off the board" so to speak. If the idea is a struggle for dominance, she just might be using her "skill" at manipulation to stack the deck in her favor.
But that remains to be seen, as it turns out the idea of "elaborate set-up by Jenazad" was the right answer.
As for Jenazad's age...yeah, there'll need to be some explanation there, especially with his father and little sister around, though it's worth noting that if he wears a mask a good deal of the time, the skin of his face wouldn't be as weathered as the rest of him (particularly his hands, which are probably a mass of callus like many experienced martial artists' are).