Help with Vicente Fernandez line?

[Henry Gale]

Hi! I'm new to this forum, but I would sincerely appreciate any help. I'm trying to translate this song, "Qué Pregunta Muchacho," by Vicente Fernandez, and in there, there's this set of lines I don't understand the grammar of, basically. I'll put in bold the part I'm struggling with, but include previous and following lines for context.

Here are the lines:

Usted, señor
De acuerdo a su experiencia
Digame si en la ausencia
Lo han dejado de amar.

1. What is the implication of saying la ausencia? Is the young man (who is speaking to his father) saying something like, "Dad, since you're going to be dead one day, I would appreciate your telling me about XYZ"?

Why would it not be "su ausencia" if the absence he's talking about is his father's? Am I totally misreading this line? Is the absence referring to the absence of love in the lines below?


2. I understand that the phrase "lo han dejado" means something like, "They have left it, they have quit it, they have stopped it, they have ceased it, they have made XYZ," but if the verb han refers to his father, why is it han and not ha? What does the "lo" refer to? Who or what is doing the action in this sentence?

3. Why "amar" and not "amor"?

Thank you so much for any help you can give me!