Why does the heat blow hot on the passenger side.

If you have a duel climate control, there is a blend door for each side. This door, located near the heater core, is designed to open and close based on the temp needed in the car. If it is stuck, you will get cold air and no heat. That needs checked. As far as the shattering windshield, I don't understand how the rear defroster would cause the front window to break.