At the onset, let me admit that most of these guys are probably much more experienced than me, so their advice may carry more weight. That being said, I've run round ball over camp coals using simple brass bag molds and iron lead pot / ladles for many years, and have usually been very happy with the results. For me, that's part of the fun of it all. Doing it the old way, outside, simple gear, simple results. (All I want is a good round lead ball, right?)
I toss bad casts into a pile that I'll melt down for recast, I use pure lead for some, wheel weights for others. Experience has taught me more than anything. (And REALLY listen about the moisture thing!)