You need to throw away the pills you are not using. Brew some coffee, stick the pills in the used coffee grounds and throw them away, outside, in the trash. Preferably in a trashcan that is far from your residence. So you won’t be tempted to get them back.You could also talk to your pharmacist about your brothers issue. The pharmacist may have a way to get those pills off your hands.
Your brother is going to come back. If the pills are gone he cannot bribe or cajole you for more. He will probably be angry. Hold your ground. Inform him that you Love him enough to not participate anymore in his destructive decisions. As for the money, kiss it goodbye.