Loss Damage Waiver simply means the rental company Waives the right to go after you for liability. That only means YOU (authorized driver) wrecked the rental car, you don't have to pay the rental company. But since you violated the rental contract to allow your friend to drive the rental car, the LDW won't apply here and you as renter ARE responsible for the wrecked rental car.
You are responsible for the rental car. You might go after your friend or his insurance company, but if his insurance limit was reached and he is unwilling to pay, You have to pay. You have PRIMARY liability.
Your own driver insurance won't pay anything since you weren't the driver.
2. Damage to the other car and driver.
Since your friend was driving, he is solely liable for the damage to the other car and driver. You are not responsible. If he had his own insurance, the insurance would pay for the other car and driver.
It is not clear what is the priority of the payment, e.g. whether his insurance company pays to your rental car first, or pays to the other driver first. I think it would be best for you to submit your claim first to his insurance company, before the other driver starts.
This is the beginning of the end of your friendship. Good luck!