I think that sufficient sleep, keeping stress manageable, eating a balanced and comprehensive diet (watch transfats and omega-6 fatty acids. The latter is found in seed oils, and it can cause a lot of inflammation if they are consumed when partly or wholly rancid). Walk or do something you can tolerate that gets your heart above 115 BPM, depending on your age it can be higher, three times weekly for about 30 minutes (helps with weight control in addition to keeping the heart fit). Enjoy socializing and hobbies, and minimize social settings, including social media, where your BP rises when you read something unreasonable or politically opposite to your views (IOW, keep your adrenalin production minimal to keep your heart rate moderated, Vagus tone positive, and your immune response from becoming frayed by chronic stress).

But really, your best ally is your mind. If it accepts the protocol to get yourself off the drug, if it makes sense to you, and you follow it without getting wrapped around the proverbial axle, I don't think you should be unduly concerned about side-effects. And, if it turns out that you must re-establish the drug for some valid reason, I don't think a resting HR near 42 is anything to be concerned about. When I was younger, and had the body of a Greek god, and could run 20km in under 88 minutes on a training run, my resting HR was near 35. That's freakin' low! But I lived. Hours 'n hours, weeks 'n weeks, years now. When you get down to 35 and you're not in especially great shape, that would be the time to sit up and take notice....in my view. However, I'm not in the health care field. I do know that your AV node will keep your heart beating at 30 BPM as the absolute bottom line failsafe if the SA node gives out for some reason. Forty-two beats a minute is quite a bit north of that. (shrug..)