Deleting photos off of my iPhone but leave photos in the cloud
No, as far as I know, there's no way to do that using iCloud, they're always kept in sync. You can either:


Ask Apple to change this behaviour: http://www.apple.com/feedback/
Use a different cloud service, e.g. OneDrive, Dropbox or Google Drive, they all provide a way to backup your photos and sync them for offline viewing when needed.