Yip, the 20% resistance reduction is just CCP’s wording.
As most know its 20% of the resistance that is taken away, not a flat -20%, that would most meta1 resistance modules a waste of slots.
No it’s not 7% for one it higher, the 14% was the combined difference of two modules with stacking penalties included.
Damage Control will negate the lose, providing you haven’t already got in mounted.
RIGs will also negate the effect, but are still subject to stacking penalties.