Psalm 82 addresses figures called elohim, traditionally understood in several ways, most commonly as human judges/rulers or members of a heavenly council. Jesus' argument does not require settling every aspect of that debate. Its force is at least a lesser-to-greater appeal: if Scripture can employ 'gods' in that setting, the terminology itself cannot make his claim automatically blasphemous.
Jesus then distinguishes himself as the one uniquely sanctified and sent by the Father and points to his works. His conclusion is mutual indwelling: 'the Father is in me, and I in him.'