Can food be simmered in an iron kettle like a crock pot? If so how high should it to be turned to?

Yes it can. How high depends on what your cooking and how long you need to cook it for. LIke most soups you start them on high to make get the gravy to thicken then on low for the flavors to blend, and cook any veggies you may have. If it is a roast or poultry you are slow cooking general rule it is about 12minutes per pound on low of course. If it is a thick meat like beef or pork it usually takes a bit longer to break-up and become soft.While poultry or seafood takes way less. IF you will be at home while it is cooking cooking it between low to med. or some ovens 1 to 3 should be fine, if you plan on leaving while it is cooking put it on the lowest setting possible.