Blowing cold air

Try feeling both heater hose, it should be hot on both if one is different could be a clogged hose or heater core. If so flush the heater core out.

Radiator coolant level is okay. Might want to bleed the cooling system just in case it has air lock see below

BLEEDING COOLING SYSTEM

Always bleed air from cooling system after replacing coolant. Set heater for maximum heat. Remove radiator cap. Loosen drain plug and remove drain bolt (if equipped) from engine block. Drain coolant reservoir. Fill coolant reservoir to MAX mark with 50/50 water-coolant mixture. Loosen bleed bolt and fill radiator up to base of filler neck. Close bleed bolt when coolant flows out without bubbles. Tighten bleed bolt. With radiator cap removed, start and operate engine to normal operating temperature. Add coolant if necessary and check for leaks.

The other thing is your radiator is exhibiting normal operation, upper hose is the return, always hotter than the lower, in a good radiator! Take cap off and squeeze the lower hose a few times, that should dislodge air bubles!

I forgot to mention the heater control valve check its operation