Imbalance I would describe as unsteadiness, a sense of unsteadiness when walking or standing as opposed to UNbalanced which always seems to me to be a feeling of exaggerated movement where limbs appear to be moving farther than they actually are.
Disequilibrium is much like Imbalance but perhaps includes a feeling that you are about to fall and is generally associated with loss of spatial awareness.
Vertigo - ‘Spinning’. has to be rotary. It is a false perception of movement either of self subjective vertigo or surroundings objective vertigo. So it can be either internal or external.
Lightheadedness (Presyncope) feeling as if you might pass out.
Dizziness is vague, general term. Definitely non rotational. And unfortunately often linked by association with anxiety and mental issues.
Sounds to me what you are experiencing could be internal vertigo but difficult to tell. With MAV self movement, moving your head, will trigger symptoms. That’s common.
As people’s interpretations of all of the above varies so much a good specialist will spend time establishing exactly what the sufferer really means because that will then help them with diagnosis. Helen