Unable to install Xcode using dmg file downloaded from Apple.com
Before doing this you need to delete the unfinished downloads and run this link in browser , which i mentioned below.
You can find the DMGs for Xcode and other development tools on https://developer.apple.com/download/more/ (requires Apple ID to login).
Link for Xcode 7.0.1 you can try this link.
Hope this will help.