I think Christians should stand firm against Islam imposing its own definition of immortality and omniscience upon us.
The bible is on our side not the side of Islam.
The omniscience of God, as defined by the bible, includes ignorance as consonant with the nature of God.
The immortality of God, as defined by the bible, includes the experience of death in the form of the God-man as consonant with the nature of God.
The bible alone is what defines truth for us, not any other belief system.
The bible gives us the truth of immortality in the context of the death of the God-man Jesus.
The bible gives us the truth of omniscience in the context of what is revealed about the ignorance of the Son in relation to the Father.
This means that Islam, or any other belief system, is wrong if it contradicts what the bible teaches.