Sell the snake... I'd say take the initiative yourself and go to the store once/week to get rats but I'm assuming you're fairly young from the way you wrote your post.
He should be eating about once/week. Feeding him once/six months is not by choice, that's how long you could theoretically wait before some intervention for snakes that refuse meals. Honestly, if you cant convince your parents to get food once/week and you can't get the food yourself for the sake of the animal sell it to someone who can take care of it.
Also, if possible try to feed it frozen rats because rats are more nutritious. I have no idea how big around he is so I can't help you with the sizing.
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