While you have the right idea, I’ll clear this up as best I can a bit (I’m not exactly the one to explain this best).
Using formulas from Moze’s Gun Damage Guide.
This isn’t quite right.
Scotching RPM’s is a crit bonus (additive to critical hits), and EM is a multiplier of 0.15 to critical damage. So if your gun does 100 damage, the crit multiplier is 2. So 200 damage on crit. With SRPM at 5/5 you get 20% more critical hit damage. That would be [100 x (2 + 0.2] = 220 damage.
EM is 0.15 x critical damage or in the example above [220 x 0.15] = 33 EM damage.
So to calculate your crit damage if your gun damage is 100 and you include SRPM, EM, and StE with a non-fire weapon against a neutral health bar:
Critical Damage = [100 x (2 + 0.2)]
Critical Damage = 220
Crit multiplier is 2
EM = [220 x (0.15 + (0.15 x 0.3)
EM = 42.9
StE multiplier is 0.3, EM is 0.15
Damage = Critical Damage + EM
Damage = 262.9
If we used your 23.4% you only get 246.8 with a gun damage of 100.
While that is higher output than your formula, your Fire in the Skag Den formula is off. I don’t believe Fire in the Skag Den receives crit bonuses. Fire in the Skag Den is just 15% of your base gun damage done as fire if your weapon is splash (at 5/5).
StE will boost FitSD by 30%, but it’s still not a multiplier to critical hits. Short Fuse will proc FitSD again though, as will grenades. PtHP will not give you the grenade critical damage multiplier to FitSD, you only get 15% of the base grenade damage.
Redistribution of course adds no damage but you mention just the effects of other skills, so yes you will still regen ammo when you hit a crit while also applying EM damage.
Consecutive Hits and a portion of the Pearl will raise weapon damage which will all be multiplied by the crit bonus, which in turn will make EM have a higher base damage to work from. The other portion of the Pearl will as well, but it isn’t weapon damage it’s a different multiplier that I am not aware of yet. Either way, I believe that multiplier will still raise EM’s output.
There are several other factors that can further increase EM’s damage, and that’s the moral of the story; It is a fantastic multiplier that is a multiplicative increase to a lot of different damage outputs.
Phew, I think I got all of that right. If not the principal is damn close and I’d gladly welcome someone correct it for us.