Yes, "leave him be" is idomatic English, although not universal because there are many variants. "Goddamn" is a colloquial short form of "God damned"; "Goddamn sled" is not a saying but simply an excited reference to a sled. When very excited, some speakers will insert "God damned" and/or "fucking" before almost any noun, or all nouns, in a sentence.
A likely source of this text is http://members.aol.com/chatarama/Episode25-TellYourGodtoReadyforBlood.htm
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