Talk to your employer about taking on the role on a “fixed term” basis of say 6 months. Tell them honestly why and see what they say. If you’re concerned about the lack in money see if you can take the 9 to 5 and supplement with the odd Sunday shift back on the floor to prop the wages up if that suits you.
In universe they are justified because Tyranids.
Tyranids won’t just kill every person on a planet, they will eat everyone, every animal, every tree, every insect and strip a planet back to the minerals and then do it again. They arent immoral because they have no morals.
In the face of that literally anything is justified even if it’s horrific.