With all skills (so +25% more base damage) the factor gets up to .484
There is only one skill that boosts guns base damage - Ordnance Expertise III. It gives
+15% not 25. Which countered by Damage Control III and its
-25% damage to hull.
As far as I know no other bonuses are applied to residual armor. Not sure about damage type. I assumed just as you do that KE is still 0,5 against it. This might be wrong.
So it will be something like:
Shot power 75 * 1,15 (OE III) * 0,5 (KE) = 43,125
Armor 1500 + 10% (AWM) + 300 (HA) = 1950 * 0,05 = 97,5
43,125/(97,5+43,125)=0,31
43,125 * 0,31 = 13,36875 * 0,75 (DC III) = 10,03 per shot
10 shots per second = 100 DPS
If you are to assume that all the armor bonuses apply to residual armor you would get +150 armor all the time and another 0,5 reduction for KE from Advanced Countermeasures I. Personally I dont think this is the case.