try this (it's not a quadcopter, so imagine the diagram 4 times!)
the drag doesn't work against the lift, the engine overcomes blade drag and puts more energy in to produce lift.
You'll also notice that in this diagram the lift is greater than the drag. However, if you change the angle of attack that ratio alters, and of course there can even be no lift at all, so then drag is larger.
Further summing forces, orientation being equal, the drag from one half of the rotary wing is more or less equal and opposite to that on the other side and cancels it out. The lift from each half, however, sums. (Many larger helicopters manipulate the blade AoA to control their flight)
$k_M$ and $k_F$ are calibaration constants - I mean you could try to use fluid dynamics to estimate them but with complex rotor shapes it would be much more accurate to measure them.
These constants simple relate the angular velocity (turn rate) to the forces produced by the rotor, it's a square relation.