An alternative option is to take a method from fig growers, who bundle up their trees to protect them from cold. The difference is that you can bundle up peaches to protect them from rain. I live in W. Washington and peach leaf curl is rampant. It takes using small pruned, or genetic dwarf, peach trees like Ponderosa (Or is it Bonanza?) or Honey Babe or Garden Gold (My varieties). I bundle up the branches with twine, each major branch being one bundle. Then I cover each bundle with a white plastic trash bag "sheath" and tie that in place as well. Keeping the rain off the buds, prevents peach leaf curl spores from getting into the buds and growing. I've sprayed the bundles before covering with copper spray but not sure if it's necessary. The bundling needs to be done in November. Then in February, I remove the trash bags and unbundle. I watch for when buds begin to swell, then remove the bags. This technique changed my peach loss from almost 100% to an overabundance of peaches. Only a few leaves were infected wtih leaf curl. I also did this with a Tri-lite peachplum, which is not genetic dwarf but is small. It worked for that as well. I plan to keep it pruned small so that the bundling is reasonably easy.

You probably reduced it some with that spray, but maybe the timing was too early/too late...or not strong enough...could try lime sulfur next year... Depends on how bad it is...if its only some of the leaves, it should still hold fruit, if its a lot of leaves..not so sure. Feed the tree with high N ferts...it'll push new leaves...try to get rid of the infected leaves.

dormant sprays of copper is effective in the winter. It is usually cured easily and seldom fatal. no worries

Depends upon how much you removed when you pruned. Peaches bear fruit on wood that grew last year.