What are the radio characteristics of communications between tower and aircraft?
They are omni-directional:  Anyone, in any direction, can hear the broadcast.

They are analog (non-digital), AM signals, so there are no bits, and thinking in terms of kbps or data-rate doesn't make sense.

These have similar transmission power to many AM radio stations.  Do you have safety concerns about local AM radio stations that broadcast baseball games?

Finally, the tower does not "control" the airplane.  The pilot on-board is the one in control.  The tower may simply give traffic directions, such as what heading to take, or what altitude is appropriate.