"If so, then from what do we need saving...."
From the power of death over us.
"...and why did He bother to send His Son?""
To destroy the power of death over man, of course. "God became man so that men might become gods", in other words, so that we might attain theosis which is our created purpose.
Is this different from sin? I always thought that the Father sent the Son because He cared enough about something to make the effort. But, you said that God was indifferent to sin.
"God became man so that men might become gods", in other words, so that we might attain theosis which is our created purpose.
I must admit that I am completely unfamiliar with this idea. We are to become gods? Is there any Biblical support for us becoming gods?