Cast 4 balls, and they look...odd?
I'm with Phil Coffins on this one
The lead in your pan is way too hot, it's "oxidizing". aka; burning
You can flux as much as you want,, but ya have to "skim" the crud from the surface,, that's what fluxing is supposed to do,, make the impurities float.
Ya scrape/skim the nasties out of the pot. (that's hard to do when it's the pure lead itself that's scorched)
Your mold won't cast proper cold, once you develop a "cadence/rhythm", a series of 15-20 ball will get the mold (and you) in sync with a proper temp,, it's about timing, again a "cadence".
(those first 15-20,, go back in the pot next time)
I struggled with the same "temp" learning curve when I first began. I finally broke down and bought a casting thermometer, when I used the device to see where I actually was and got the temps where they should be, it was much easier, much more successful.
Within a few months, the thermometer use languished, it became easy to see the condition of the lead in the pot.
There is an apparent "visual/apearance" to molten lead that changes within the proper range that becomes easy to identify once you learn it.
I like to run mine a little on the hot side,, 740-780 for my best results, I cast in early spring or fall when outside temps are in the 40-50's