So officers DO NOT have a duty to follow ALL orders which are given to them as stated above.
No, but like I said, officers are not obligated to follow illegal orders.
Janeway's orders WERE LEGAL. You can debate till you're blue in the face if they're MORAL, but they are LEGAL. There is a difference.
So explain to me how arbitrarily ordering a crew-member to their death in a non-emergency situation is legal.
Because Janeway needs Tuvok and Neelix back.
No one should be forced sacrifice his or her life for another.
Not until they join the service, anyway (real or fictional). Then they most certainly can be forced.