over-investment
1. Does "over-investment in the signifier of the smile" mean "an unusual amount of attention to the subject of smiling"?

2. Does "his mother’s smile to himself" mean "Leonardo's mother smiling to him"?

3. Does "beyond the object of the smile as such" at the end of the context mean "beyond the usual and common meaning of smile"?

Context:
In this model, even Leonardo’s enigmatically smiling women could be seen as the repetition of a trauma and an over-investment in the signifier of the smile. Rather than restoring his mother’s smile to himself, Leonardo could be seen as being compelled to repeat it as a moment of loss, which generates a desire beyond the object of the smile as such.

Question

over-investment
1. Does "over-investment in the signifier of the smile" mean "an unusual amount of attention to the subject of smiling"?

2. Does "his mother’s smile to himself" mean "Leonardo's mother smiling to him"?

3. Does "beyond the object of the smile as such" at the end of the context mean "beyond the usual and common meaning of smile"?

Context:
In this model, even Leonardo’s enigmatically smiling women could be seen as the repetition of a trauma and an over-investment in the signifier of the smile. Rather than restoring his mother’s smile to himself, Leonardo could be seen as being compelled to repeat it as a moment of loss, which generates a desire beyond the object of the smile as such.

Answer

My god, the guy who wrote that is nothing if not obtuse!! Yes to number 1, no, it's Leonardo trying to regain/recover the smile/love of his mother. To 3, I think the meaning is that in trying to recreate the lost smile of his mother he in the end is trying to recapture something more than just the smile. Heal a loss that the smile symbolises.