People pay real money for smartphones.

The absolute values for heart rate vary from person to person and change as you age. But I do notice that my resting heart rate slowy drops a bit as I get fitter (e.g. during a marathon build) and will rise more suddenly if I am getting sick or not getting enough rest.

I don't really pay much attention to the heart rate zones on my watch, but I do have a pretty good idea e.g. where my 5k race vs marathon race vs really easy run heart rate lies. This can be one piece of information along with perceived effort and pace to decide if I should be able to push a bit harder on a hard run or take it a bit easier on on what is supposed to be an easy run.

Start out slow (no, slower) and don't be afraid to take walk breaks if you need them. Try your best to get out at least a couple of times every week (but not every day) for at least half an hour or so. Progress will take time, but you will find that you will gradually be able to go farther and faster.