Wouldn't "ní ritheann d'athair mar tá sé leisciúil" make more sense semantically? It's his laziness that causes him not to run, and not the other way around.
Má should be translated as "if he doesn't run" as well as "as he doesn't run." That may be the way it's said in British English, but I don't think I would have ever used "as" there in America.
The sentence has mar, not má. (Or maybe it had to be corrected?)
Ghalldaigh siad an téarma.