High Pulse Rate, Low Blood Pressure

Is anyone else dealing with this problem? After triple valve surgery in mid-May, I've been on a number of pretty strong meds. This far out, my medication has settled into a pattern of metoprolol, lasix, atorvastatin, potassium, eliquis, and various supplements and vitamins. I have on-going issues with a right pleural effusion, and for that I was prescribed colchicine in late September. I started taking and recording my vitals daily starting in July, and have seen my resting pulse rate creep up from the mid-80s to the low hundreds. Last I knew, before my surgery, I was usually in the 70s. Now the slightest exertion leaves me feeling faint and winded. If I check my pulse at that point, it is always in the 108-112 range. Most of the time when I check it while resting, it hovers around 98-100. At the same time, my blood pressure has been trending downward. It has never been high. "Normal" for me pre-surgery was 110/70. Now I average around 90/50. I consulted with my cardiologist when I first became alarmed by the high resting pulse rate...back when it was in the high 80s. She asked me to wear a heart monitor which I've been doing for almost a month now. She tells me there's no evidence of afib or arrhythmia. That's good news. She suggested that I try increasing my metoprolol from 25mg a day to 50mg. Thing is, that's a beta blocker and has been known to lower blood pressure. I'm trying to decide if I want to risk feeling even more faint than I do now. I have two questions:
(1) Would you increase the metoprolol if it were you?
(2) Any idea what negative effects are caused by rapid heart rate? I know it makes me feel awful, but is it likely to cause heart attack or stroke? I can't get any clear answer to that question from either my doc or my reading.

Thanks for any recommendations you care to share.