Beta blockers is a proven medication that improves survival in those who have suffered a heart attack, have coronary artery disesase, or
heart failure. If there are indications
for this, then it is usually a good idea to be on one. There is no absolute value of heart rate that is too low but the general rule that is accepted is you are symptomatic, then the dose should be decreased.
Increasing the amlodipine to 10 mg is not a bad idea as you still have room to go up on it.