Some questions (Man, precision and other)

[Beorne]

I'm a newbie and I'd like to understand more deeply the mechananics of this game.
How the precision stat of missile weapons interact with the target? the target rolls against def or what? And the precision of spells rolls against something to hit (apart the spell resistance if applicable)?
What is the precision loss due to diatance?

I take for now the Man - Last of the Tuhatas theme: I noted that my sacred infantry is blurring all the times during combat. I thought it was an air shield created by the blessing (i'm a nature-air pretender). But It appears that it is in even before the blessing. Are my units always air protected? If so, how do I know the additional benefits of spacial themes?
How air shield work? Is the miss percent is calculated after the missile hit?

Thank you