Deep, you might really benefit from taking niacinamide and the mineral supplement lithium orotate (which is NOT the nasty rx). Niacin speeds up the comt enzyme, soaks up extra methyl groups, and helps stabilize things. Those 2 supplements together are helpingpeople get off their rx meds, from what ive read it seems it actually works better for some or most people, and you are a prime candidate. Its worth a try.
You are correct in assuming your body is making less of those neurotransmitters, but you are still more likely to have too many compared to a person with no comt mutation and are considered to have a higher risk factor for depression, anxiety, bipolar, etc. The good news is, its very treatable with supplements.
Low blood pressure can be caused by alot of things. It sounds like you may have a case of adrenal fatigue going. It doesnt mean you dont have an ammonia problem when you eat sulfurs.