Fatigue from itemspells ?
 

I didn't test around too much there but i remember that an assasin got only iirc 5 fatigue from casting 1 skeleton / turn by the misc item that does this .

Is there a general rule how high fatigue is from spells casted via item like fatigue = 1x melee fatigue or is it more complex ?

Re: Fatigue from itemspells ?
 

Some spells cast by items cause fatigue (not all), and when they do it's always 5 fatigue points.