Got bullets cast. Have been doing all the above in my garage, w/the big door open, for ventilations' sake. A little breeze does get in. Apparently that's enough to cool the pouring nozzle on the furnace.
So, when the furnace pour slows to drips--having fluxed, and using clean lead in clean pot--I turned on a propane torch and gave the nozzle a shot or 2. Nozzle responds by un-plugging and running great.
Cast up a nice mess of .452 semi-wadcutters.
Following day I set up my Lyman lube/resizer--it's the old model, and they say it doesn't fit on their heating pad, but I got it to fit anyhow--and sized the bullets to .451 and lubed with Orange Magic.
Thank you one and all for all your helpful thoughts and advice!