1), You can use a widget called A-Volume, that will allow you to do that
2) that is a tough one, like you said if signal is bad, then your only option is to monitor signal strength and areas and either turn phone off if you are in those areas for long periods, or put your phone in airplane mode during that time.
3) this I am not sure about, but maybe Pandora has a settings in it that has the volume turned down, using the above widget might tell you this once installed.
4) Maps is one of those finicky apps, depends on the device, you can uninstall the update, then re install it, and then try rebooting your device, also make sure not too many apps are running in the back ground when using maps, as maps uses lots of resources and will drain your batter, hit the recent app soft key button, and swipe away the background running apps. see if that helps