What exactly happens when I try to maintain the flare when coming to a hover?
If I attempt to continue maintaining the flare, attempting to come to a stop, I will sink and if I don't do anything about it, I will hit the ground. Why?


if you continue to maintain aft cyclic after the flare, you will hit the ground because some of the lift which is being generated will be used to fly the helicopter backwards, and you won't have enough power in to both maintain altitude and also maintain backwards flight (which is what you are commanding with aft cyclic). This is why we level off after the flare: to use all the lift in the vertical direction.

Its the exact opposite of take-off: if you are in a hover on the runway, and push the nose over to the 60KIAS nose-down attitude, you will descend into the runway.

Although I have never tried it, I imagine that at the peak of the flare, if I add (a lot?) of power without changing the attitude (much:), I will not descend into the runway, but rather I will start to fly backwards.