I would leave the simulator in the Xcode package, but drag it to your dock to easily launch it. Or make an alias to it and place that alias in what ever spot you want to launch simulator from.
The option to download iOS 4.3 simulator is available from within Xcode. You can find it under Preferences > Downloads. Just click on "Install" and you might have to enter your Apple ID credentials.
If you don't see this option, you could try removing your older versions of Xcode and installing the latest one from the Appstore. My version is 4.3.2.
Best Answer
Xcode 7 does not support iOS 8.4 and earlier.
Xcode 6.4 does not support iOS 7.1.2 and earlier.