I very much doubt that two cylinders "are out" because they are running lean.
It is much more likely that two cylinders have fowled plugs due to the wrong shutdown drill.
I see that the "dont lean below Bla bla bla" people have got to you, the Lycoming engine manual states that you can lean at any altitude when the power is set at or below 75%. leaning will save about 20% fuel burn.
As for question 4 with no EGT indicator you have the drill more or less correct
I have two C152's that we lean that way and get a fuel burn of IRO 23lts/hr.