Same age and gender as you and my watch says my resting HR is 50-60, walking is same as yours. I jog every day and walk around a lot at work, though I do have some hereditary chronic conditions. I will say that I naturally walk extremely fast, even when not in a hurry. I usually have to pass almost everyone on the street, so it’s almost like a jog. Maybe you do the same.
Mine (SE2) did after 10.1.1 (the other ones didn’t affect it at all)! It used to drain by about 2.5% an hour overnight, and now it’s draining 1.5% per hour at night. I think daytime went from 3%/hr to 2.5%/hr. I used to charge it twice a day - once when I got home from work, and once while getting ready before work (just a quick top-up to 75%), but I think with this change, I can just do it once a day.