Sorry... I don’t follow.
You asked if it was EVER OK. Yes, of course there are circumstances that can make it OK. You’ve already said as much yourself.
"Is it permitted for any reason directly and deliberately and intentionally to kill an innocent human being?"
The adjectives and adverbs are really important here. To examine the variations:
(Examples: a deadly aggressor in a criminal or wartime situation, or a person justly convicted of a capital crime. Answer: under some conditions, yes.)
(Examples: performing a hysterectomy on a pregnant woman who has uterine cancer, even though the baby is not yet capable of survival outside of the womb. Bombing a Hamas rocket-launcher site even though it's on the roof of a family residence. Obliterating the military and industrial and port facilities of Hamburg during WWII, even though the resultant firestorm will foreseeably spread to civilian areas. Answer: under some conditions, yes.)
(Examples: Aborting a handicapped baby. Killing prisoners of war who have surrendered and have been disarmed. Killing everyone in a city indiscriminately. Answer: no.)
One last question: does it sometimes happen that the situation is complex and changing rapidly, you're not sure of the facts, the options are all dreadful, and you have to make a quick decision under extreme pressure? I'm sure that happens. We must try not to kill the innocent. May God have mercy on us all.
Trying to work through this carefully. What say ye?