
Smaller than a pack of cigarettes. The dial is continuously adjustable not click click click. Find a place to hide it under the table.
There is no "piece of cake" solution to modify your existing fixture.
A three way click click click switch needs three adequately sized resistors chosen and added inline from each switch terminal to the LED.
Home dimmers and dimmable LED's are a color of a different horse...
Dimming affects the LED driver that drops voltage from 120 vac to whatever DC voltage the lamp demands. The word affect means the wrong type of dimming gizmo can fry the "driver". You do not have this issue to begin with.