A500 Yes, using channeling for healing is an inoffensive use of the ability (since you can't heal and harm at the same time).

A501 Casting darkness on an area with light, dancing light, or both, lowers the areas of normal light to dim light, and areas of dim light to darkness. Darkness is a 2nd level spell, so it should be applied after any [light] effects of lower level. If you use darkness to dispel one of the effects, one of them would still remain.