1) I would expect HR to be more stable as you’re not taxing your system as much and you can adjust your intensity with more margin to stay in Recovery zone. Of course, over enough time HR drift should still occur as you eventually get more tired.
2) No I would expect it to be easier because the effort is easier
3) Again, no I would think since you’re training as such a low intensity (65% max HR…assuming that’s well into Z1 if not even lower into the Recovery zone) it should only take longer for HR drift to present itself. See #1.
4) What is “average?” I advise against comparing oneself to others as everyone’s genetics, training history, self-care, nutrition, rest, injury, etc is different. As you develop a larger Z1 you will be able to run faster at lower HRs. This will be a matter of personal discovery for you to determine what HR you can run at.
(side note…even how 1 person defines “running” is different from how another person defines “running.” 5km/h? 10km/h? 20km/h?)