Possible meanings are 1) "Yahweh is the one who gives me strength" or 2) "Yahweh is the strong one who protects me." (See: [[rc://en/ta/man/jit/figs-metonymy]])
Moses calls Yahweh his song because Yahweh is the one he sings about. Alternate translation: "the one I sing about" (See: [[rc://en/ta/man/jit/figs-metonymy]])
Moses calls God his salvation because God saved him. Alternate translation: "he has saved me" or "he is the one who saves me" (See: [[rc://en/ta/man/jit/figs-metonymy]])