The iPhone and iPad will not pair with Bluetooth. They are not designed to do that. While they both can share some information over the air, such as AirDrop, they need to have Bluetooth turned on, but not paired.
As far as text message forwarding, that needs to be turned on on the iPhone, and the iPad needs to be selected on the phone for it to receive those messages. There is not a setting for text message forwarding on the iPad. One other thing you need to check is to ensure that both devices are signed in with the same Apple ID. Check this support document to ensure that you have all of the settings correct, Use Continuity to connect your Mac, iPhone, iPad, iPod touch, and Apple Watch - Apple Support