I am not an expert by any means. I hope someone else chimes in as well. My peach tree experienced leaf curl for the first time last year. It's caused by a fungus. I read to use the copper spray in the fall after all the leaves have fallen off the tree. Leaf curl will eventually kill off the tree. Last year I plucked off the worst of the leaves and in the fall I sprayed it with copper spray. I'm keeping my fingers crossed for this season. I don't have an answer for #2.

Maybe this info and control sheet on leaf curl will be helpful: Peach Leaf Curl