what is a reasonable amount of condensate water produced by my pump?
It doesn’t seem possible to me for the furnace to produce excess condensate, it’s just a matter of how much hydrogen is in the fuel and how much fuel is burned.  The water heater at least has a source of water - if there’s a leak in the heat exchanger it could combine with the condensate.  Can you move one of the drain lines out of the pump, and drain it into a bucket to see how much you get from that source?