Not to alarm you, but I’d be calling that cardiologist’s office to get in without a delay. Given the history of your mother’s cardiac arrest at a young age and your drops in blood pressure/heart rate, an evaluation is really important. Low blood pressure can be the cause of your exhaustion because your body isn’t getting enough oxygen. But your exhaustion, BP that low, abnormal heart rhythms and passing out aren’t things to trifle with.
You mentioned waiting to see a cardiologist for over a year. Do you actually have an appt scheduled?

@deborah67 maybe you should go to the ER when you have the low BP or faint. Sometimes, you need to show them your symptoms when you are having them. Tell them if you are having heart symptoms, they will need to address them. Don’t be shy about saying what is wrong. I read once that if you tell your provider that your loved one (sister, son, daughter, spouse, friend or even co-worker) insists you be seen they are less likely to dismiss your symptoms. If you say you have chest discomfort or pain they are also required to check your heart in ER. It is getting harder to see specialists these days due to the shortage of Drs. Take care.