How can a man who owes "dam" for abandoning an obligatory ritual of Hajj absolve himself of liability, and is it permissible for him to appoint someone else to slaughter a sheep for the poor of the Haram these days, or must he wait until the next Hajj season?

Whoever omits an obligatory act of Hajj must offer a sacrifice (dam) to be slaughtered in Mecca and distributed among its poor. If the pilgrim forgets or does not know the ruling until after returning to his country, it is permissible for him to appoint someone to buy the sacrificial animal and distribute it on his behalf in Mecca, because the intention is for the people of Mecca to benefit from it, and this is achieved whether the one who slaughters the sacrifice is its owner or his representative.