1. Sustain life without imported energy source?
Well, there's nothing to say that the black hole cannot have a companion star. There are plenty of stable configurations possible. In a non-circumbinary planet, if a planet's distance to its primary is below about one fifth of the closest approach of the other star, the orbit can be assumed to be stable. So the world could still have an active sun.
That is a much more reliable source of energy than Hawking radiation, which is orders of magnitude smaller than the current levels of the cosmic microwave background. In other words, black holes are much, much 'colder' than an empty dark cosmic sky.
Radionuclei inside the planet can also help sustain life, but I strongly suspect that the amount of biomass the low concentrations of radionuclei would produce would not be very large. Still, you could look into natural nuclear reactors, which would be a pretty cool idea, assuming with some reason that orders of magnitude larger uranium deposits were generated in the original black hole collapse.
2. What is the best and safest orbit for life?
Orbiting a black hole (assuming it is a quiescent one, without a giant feeding accretion disk) is no different from orbiting a regular star of the same mass in terms of the gravitational effects on the orbiting body at moderately large distances such as the radius of Earth's orbit for a hypothetical sun-sized black hole. Orbit very close (a few tens of thousands of km) and the tidal forces caused by the gravitational gradient would probably tear the planet apart.
If the black hole is actively feeding, it will have deadly magnetic fields (these can die down if it is inactive, i think), and a horrible flattened accretion disk spewing radiation like there's no tomorrow. Any planet near the disk would be subjected to sterilizing radiation. Worse, if it's a captured world, it might be in high enough off the orbital plane (right ascension, was it?) to get into the path of the jets, which might even be strong enough to eventually liquefy the planet and blast the debris away.