To use exposure values (EV) instead of absolute apperture numbers set the center f-stop parameter to 0 in the viewer setting.

A multiplication of 1 is the same as an exposure of 0 with the exposure node. The multiplication node simply multiplicates the image by the value in a linear fashion. An increase of the exposure with 1 exposure will double the light. This means that an increase of exposure by 1 means that twice as much light is introduced. To get the same effect with multiply node we need to multiplicate with 2 to get the same effect. The increase of exposure is with other words quadratic.

To toggle between viwer inputs hit the up/down keyboard arrow.
To step 1 keframe back/forth use right/left arrow. use modifier key shift to step 10 frames. the alt key to go end/beginning.