It depends what you think an agent is there for. It's more than just facilitating transfers, and can be for mentoring and general career guidance.
Zlatan is still a top professional, whichever way you look at it, as per his career length and the way he's recovered from an otherwise career threatening injury at a late age.
Absolutely. Having never lived such a life it’s hard for me to imagine ‘needing’ such a figure I guess. These people aren’t complete idiots so they obviously feel he contributes massively to their career, just seems weird, especially in Haalands case. Well off, obviously talented, probably trained like a pro from a small child and given every opportunity, Dad was a pro himself etc