I wonder why black holes can't suck up dark matter? Or, if they did, would the dark matter have a distinctive X-ray spectral signature or emissions in other channels? Clearly the interaction feeding the thing is supposed to be gravity, and by hypothesis dark matter does provide some gravitational pull.

On more mundane points, the galaxy does not emit "x-ray jets", that radiation will be more uniform. The galactic center may emit physical jets that excite x-rays along their path. Our galaxy also sports a central black hole, which might have been just a bright a few million years ago as the ULX of Andromeda ... but has now sucked up all the local star victims and feeds at a lower rate.