I'd build the hottest fire you can to burn off as much paint as you can.
While it's red hot mist the inside with a hose and let cool. Than wire brush off as much as you can and burn it out with a hot fire a second time before cooking anything.
You'll be fine after a few good hot burns.
Use heavy duty oven cleaner. It will strip paint. It’s messy so make sure you prep the area properly. Let the oven cleaner soak a few hours. Keep it ‘wet’ with the oven cleaner. Clean with warm soapy water, rinse, and then start a hot fire for final step.
No.He also used acetone to prep the metal on the inside of the door before painting it, this gonna be an issue?