How can I lock my model to pivot seamlessly with the access of the HDR background when rotating camera? Currently it floats of the ground when I rotate the camera.
The HDRI is projected on a sphere, which your model is free-floating in. It's not possible to create a relationship between the active camera and the model in relation to the HDRI.
My suggestion is to use a backplate instead of having the environment visible, unless there's a specific use case you have in mind.
What are you trying to do?