Excel Formula for multiple conditions

Hi, 

I have built the following selection tool:

My formula that I require help with calculates the value seen in the cell to the right of "Operating Capacity [BTUs/Hr] (w/o Pump)":

=IF(Series="A",INDEX(Operating_Capacities,MATCH(AmbientTemp+25,CondensingTemps,0),MATCH(FLOOR.MATH(SetPtTemp,5,1)-25,EvaporatingTemps,IF(FLOOR.MATH(SetPtTemp,5,1)-15>55,1,0))),INDEX(Operating_Capacities,MATCH(AmbientTemp+25,CondensingTemps,0),MATCH(FLOOR.MATH(SetPtTemp,5,1)-15,EvaporatingTemps,IF(FLOOR.MATH(SetPtTemp,5,1)-15>55,1,0))))

The defined cells are as follows:

Series = "Series"

Operating_Capacities = range of cells in the table below selection tool

EvaporatingTemps = cells with values 10 : 55

CondesingTemps = cells with values 100 : 150

AmbientTemp = "Ambient Temperature"

SetPtTemp = "Set Point Temperature"

If series A is selected, -25 is subtracted from the Set Point Temperature. In addition, if the temperature is over 80, it defaults to 55. 

If any other series is selected, -15 is subtracted from the set point temperature. If the new temperature is now above 70, it defaults to 55. 

What I have to add in is the following:

1. If the form control, "50 Hz" is selected (a.k.a., true), the operating capacity has to be de-rated by some constant. For example: New Operating Capacity = Old Operating Capacity - ("Some constant" * Old Operating Capacity)
2. Furthermore, if the form control, "Cleanable Heat Exchanger 'Yes' option is selected, -35 has to be subtracted from the setpoint temperature. 

I realize I cannot have more than 7 nested IF functions and would greatly appreciate any suggestions on how to rearrange my main equation to include these 2, new additional parameters.