Thanks Hokej. I do subscribe, and I do set the number of ends. This sets a maximum number of ends - not a minimum.
My suggestion was to set a minimum number of two.
Scenario 2 in my original post happened yesterday. Four ends set, first end I had hammer. I had 5 stones in the house, opponent had 2 both lying "shot". I had an "easy" double take out, possibly for 5 or 6. Opponent quit before I played my final shot, so I didn't get to play it! Outcome was that I got 1, and 1+1+1 for the three unplayed ends; 4 in total. None of us really play for points, but anything that deters unsporting behaviour (which happens all the time) would be good. Had I been my opponent I would have stayed, then posted "good shot". That's called etiquette....