Could my furnace be leaking due to condensation neutralizer?
To me it looks like the drain line is plugged causing the condensate to build up in the air handler. Once the water level is high enough it finds a way out. 

You know your pump is working but now you need to make sure to clear the line from the air handler to the pump. It is quite common for dust and spores to develop blockages in the tubing and this creates the problem you have.

There is 1 more possibility that a low Freon charge could be causing the evaporator to ice up and possibly water dripping down the side wall is causing the leak but I would be clearing the drain tube (this is quite a common thing).