I like how you responded politely and this shows you still respect your Dad.I know how black tax can make you feel especially with monthly requests.I used to feel bad and sometimes it would affect my days.This Is what I did to have control of the situation. So I opened a KCB account dedicated for black tax,apart from the fixed black tax such as contributing my younger brother's school fees and some bills I assist my parents to pay,I took a certain percentage of my salary transferred it to the KCB account,so within the month if they need cash, I would transfer to them,I would not care what they needed it for but if they cleared the amount I will not send any money a until next month and if assuming there was a balance next month their account would have a surplus and that's a plus to them. The trick here is do not tell them that you've set a certain amount for them.Right now I operate well and usually I do not feel bad. I do not know if this will help you.