1. Paint will likely burn & smoke, unpleasant at least and dangerously toxic a possibility. Try to remove the paint with an appropriate solvent first.
2. The melting point of aluminum is 1,221* F and hazardous for melting lead. Altho the pot itself may not melt, it might weaken enuf to break with the weight of the lead. On a gas burner, I did manage to melt an aluminum pot (with lead) when I left it sitting too long.
3. I have been unable to LADLE pour your listed sizes even with pure lead at high temperatures. Mystery scrap lead might be even harder to pour. You will probably need a good bottom pour melter and MAYBE some cleaner lead. I'm guessing you got some sheet lead, which in my experience is usually decent quality for scrap. Pipe lead is a bit iffy, but likely alright.
I'll let others comment on using a kitchen stove for this purpose.