Bp drops sometimes due to dysautonomia and i get a mild angina from lack of blood to heart, sitting down relieves it. am i at risk of ventricular tach?

Yes: Myocardial ischemia (poor blood supply to heart muscle) from low BP could trigger ventricular tachycardia, but it is extremely rate in case of dysautonomia. If there is low BP from dysautonomia you will feel dizziness or chest pain or experience syncope which makes you rest or take a supine position. These postural changes adjust your BP rapidly. Heart regains its blood supply quickly.