I was cleaning my microwave and wiped the top and the lining peeled away like flaking paint.

Microwaves just aren't that expensive, and they are so light now you can carry one under one arm.
Even if it isn't leaking microwaves (supposedly that protection is very good and has been for years) why not get a new one? Higher wattage is handy too. Just don't share the circuit with a toaster.

The paint will crack and peel if you heat a lot of things uncovered. The heat and stem wear away at the finish over time.leaking microwaves will not cause that.

By testing