get a new radiator
mine was about $120 from autobarn

six 10mm bolts (with AC installed)
or
four 10mm bolts (without AC installed)
two hose clamps

do yourself a favor and DONT START THE CAR ANYMORE

its hunting for an idle because the fast idle (extreme cold warmup) is determined by antifreeze going thru a hose into a sensor under the throttle body...when there is air in that hose (like your situation), the engine thinks it -10* degrees and starts raising the idle to raise oil pressure and help warm the engine faster to protect itself.

change the radiator, add coolant, and monitor the level in your overflow tank (near battery) for a few days until the engine works all the air out of the system.

~boomer