You can melt it down, and pour it out in thin layers in an old pot. Then maybe you can add in small amounts of it to good lead later. The advice you got about keeping the mold hot is sound too. Sometimes I dip the corner of my mold into molten lead to heat it before I even start using it. I've read that heating lead too hot can harm it, but I always heat mine to the max. The crap that forms on top can be removed with a spoon. I use a wooden handled lead ladle and put the scrap in an ashtray to cool, to be discarded later. Some molds, like your hook barb mold, can be finicky, but I believe the good lead will improve your outcome considerably.
Good Luck!