On vRA 7.5 it's possible to "REMOVE" a machine from an existing "Deployment" from vRO without destroy the Deployment ?
Yes you can run the Destroy action for an individual machine. However it will not clean up child components of the resource, including running Uninstall tasks of software components. It is not recommended to destroy individual machines.
On vRA 7.5 it's possible to "ADD" a machine from an existing "Deployment" from vRO ?
Do you mean add an existing machine to an existing deployment? If so, no you cannot do this. If you mean add a new machine to an existing deployment, Scale Out may meet your needs.
If you mean import an existing machine to a new deployment you can import vCenter VM's (does not support software components or composite blueprints) but you cannot import Cloud machines.