Almost every place where someone gets hung up on Demon Abilities relates directly back to where the text for the power states a game world, casual relationship. (Range in meters, duration in minutes, et cetera.)

Get rid of them.

Here's a clearer way of stating things like 'duration of the power' and so forth.

In Sorcerer, nothing is ever instantaneous, eternal or infinite. If the notion of time and space becomes relevant to the conflict at hand than these factors are limited by a Demon's Power. [1] (See also the Ranged Ability for more on extending durations and so forth.)

Is there a limit of 1 demon ability actived per turn per user? If a character has, say, Armor, Cloak and Protection conferred upon him, can he activate all of these in a single action, or would he have to spend 3 rounds preparing for a fight to ensure that these 3 abilities were all up and running before a fight?

Since they don't require rolls to activate, the demon can turn them on simultaneously. However, that's not a "free" action; if it happens during combat, it (turn all of them on) is a time-requiring action like any other. One may usually consider a demon who's getting along decently with its master to have the brains to kick on these abilities just before the fight/confrontation starts, removing that particular problem. [2]

Note: every use of any demon ability counts against that demon's fatigue -- even 'passive' abilities such as Armor. If a demon has Armor, Fast, and Special Damage, it might be getting three points of fatigue a round.

All abilities do fatigue the demon, but Sorcerer isn't based on "physics;" it's about seeing the ability happen, not about whether it's "turned on," So if that demon were not hit in that round, the Armor wouldn't cost it any energy. [3]

A demon's damage penalties do not affect its power ratings on abilities. (I.e.: A Power 6 demon with Vitality has its Vitality rated at 6, even when wounded.) Conversely, a Punish Ritual does reduce Ability effect.