ECG only showed low pulse rate (Bradycardia) so we can assume that ther is no sign of heart attack.
BP is fine on sitting but becomes low on standing. You are already on hypotensive agents ,,Atenelol and amlodipine and feeling faint.
Can we associate the low BP with the bradycardia as shown on ECG?
Answer....yes we can.
Hashimoto's Disease (underactive thyroid) will give you low pulse rate and low BP.
I agree with your doctor to reduce you BP tablets, BUT you also must have your thyroid investigated to eliminate underactivity.