Were it I, that would not be in my lead pot. I have an old cast iron pot that I use for smelting, and I would be doing about 40 pounds at a time with a big handful of sawdust followed by a candle stub of wax, stirring constantly for about five minutes. I'd flux it and scrape out the scum about three times before pouring it into ingots (may have to flux and clean it four or five times to get the crud out.) I would not waste any tin on the melt until I had it at least reasonably clean
I'd not even try a boolit until I had the melt clean.
The boolits you show are very likely cast from a really cold mold. I'd preheat the mold before casting and then I'd cast a freaking bunch before I even looked at a single boolit.