“Is it not catholic teaching that God is IMmutable?”
I’d say the teaching is that God does not change unless he desires to do so.
“that Scripture is inerrant, Scripture which says that ‘flesh and blood’ cannot inherit God’s kingdom?”
You’d deny bodily resurrection? We see after the resurrection of Christ in the Gospels, that he does have a resurrection body, which is the flesh purified. That he eats and bears the grevious wounds inflicted on him from the cross, and yet no longer suffers.