Hair tests for mercury toxicity are considered unreliable.
Swallowing a filling is not anymore dangerous than having it in your mouth and it is usually excreted in 24 hours.
Dizziness/vertigo is not a typical symptom of HG toxicity but Hg can affect people in different ways.
Usual symptoms are depression,anxiety,anger,emotional instability,sensitivity to light or sound,excess salivation,brain fog,etc.