I am a little confused by this:
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If receiving the love of the truth would have saved them hypothetically, doesn't this necessitate sufficiency for them?
How does "the love of the truth" save anybody? You quoted from Jn. 3:18 which speaks of believing on the only begotten Son of God and not on loving truth. However, let us say that this is the truth which is being alluded too. I will have to question how anyone could love the Truth unless it was given to him. Only the elect are given this through regeneration. Hence, it is accurate to say that the atonement was indeed sufficient for the elect. Nothing more is needed for this as the atonement of Christ is completely sufficient for what and whom it is intended.

The Chestnut Mare