Can I substitute yogurt for sour milk in this recipe?

that should be "can also add 2 T. white vinegar"......

yes. and you could also add 2 white vinegar to 1 cup minus 2 T. room temp whole milk; let sit 5 minutes and use in recipe. The milk should have curdled a little.

Yes for sure! You may also substitute sour cream + some milk(if it is too thick) for sour milk. It will be delicious!