I'm currently reading a fascinating book on East Anglian magic and folklore. It details everything from keeping mummified cats by the hearth to charms to trap 'imps' in bottles. People were just as likely to consult the local cunning man or wise woman as pray in church.
For me intent is key. I've mentioned before that I have no issue with destroying photographs. If however I deliberately scratched a face out of a photograph with the intent that it would hurt that person I believe it would have an effect because of what it would release within me.
I don't see the point in praying for things that go against the natural order. Asking for better health won't happen if you then eat pizza on the sofa, but if a prayer or ritual then focuses one's intent to eat better and be more active then it has done its job.
Wrong again! A curse or action won't harm a believer but it could come back on yourself. Christianity, is about forgiveness not revenge. It about the act of forgiveness and your last point is pretty moot too.
40 years the LORD God kept his people in the wilderness. There clothes and sandals never wore out. They had mainly manna for food and they were all healthy when they came out into the promise land.
Jesus Christ spent 40 days and night without food and water and in the desert.
He did not die and angels tended him after he was tempted by Satan. He offered him many things but the truth is...Man shall not live by bread alone but by every word that proceeds from the mouth of God.
It isn't what you eat that kills you it is your lack of knowledge about God.