The range on E6B is not your actual range you can travel. It's simply how many mph you're doing times how much time you have left. It doesn't take into account altitude.
A "ring" is a dumb idea frankly, because it would be useless and not accurate. Just know 1 sector = 25 miles across. If you're low on gas keep all the alt you can. At 30k you can glide over 3 sectors with no gas left. If you're on the deck, spend some gas climbing very shallowly so that when you run out you can glide her in to land.
There are tons of ways to lean out a trip home, but the best one: TAKE MORE GAS WHEN YOU ROLL!