As with all good questions, they should be answered with truth.
Here the question is, does the "world" of John 3:16 refer to all of fallen mankind, or just to those chosen for salvation? It refers to fallen mankind, as it does in almost every case where John uses the term. In a few places, world refers to the fallen value system of fallen mankind.
Love grows in the garden of commitment, love manifests itself with commitment. See 1 Corinthians 13 for a more robust treatment.
When Jesus says, depart from me, I never knew you, is this tantamount to saying I never loved you? I think not. He died for us when we were yet sinners, therefore we were not elect when He died for us. Scripture says (Romans 8:33) no charge, such as sinner can be brought against God's elect. He died not only for the sinners who would become chosen, He also died for those who would not, such as the false prophet of 2 Peter 2:1.
So when scripture says God demonstrated His love toward us, when He died for us, that death demonstrates God's love toward all of fallen mankind.
Turning next to the question of if God's love stops when the lost perish and are consigned to Hades, my answer is not quite. God still treats the lost to justice, taking no pleasure in their punishment. But they are no longer considered potentials for redemption, so love diminished seems all that can be supported from scripture.