I think 'maximum' refers to the fact that you could get less time if it was destroyed. The Special sections both refer to uses per day, so I think you need to take it multiple times if you want it more than once per day.
Unseen servants disappear if they go beyond the spell's range, and the Trickery Devotion image has "all the same limitations" so I would say it disappears if it goes more than 30ft away from you. Unseen servants can only be destroyed by area attacks, but I would say that if someone tries to attack it in combat they waste their attack, but everyone who sees it knows it's an illusion thereafter.
If you are still interested with those caveats, I will allow it.