If the volume down is stuck that is your problem as to why it is stuck reloading in "Safe Mode". You really need to get that key unstuck as even if you can get it out of "Safe Mode" using the following info, it may well go right back into it when you restart the device.
Try this...
Use the "Status Bar" to turn off "Safe Mode'. Pull down (swipe) the "Status Bar" of your phone. Now tap the "Safe Mode" button. This should turn "Safe Mode" off. Now your phone will automatically restart, so that it boots up out of "Safe Mode".