My teen has moved out and I can't afford to support him?

I am having problems financially and my teen moved out age 17 I try to give him 60 a week he doesn't pay any bills as he stays with his grandpa but I have to supply food, I don't really know if I am wrong for feeling this way or if I should be trying to give more. I only currently earn 1600 a month and have a mortgage of 425 and two other children, bills, car etc
Would you think I need to give more or less or what?

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