I'm not sure if Old Gods from Oblivion Wars are the same as Outsiders.

Because if Carlos still felt empathy for Harry, he wouldn't have pulled what he did on the beach.

This is not a question of empathy but of trust. Empathy is skill/ability of one's perception not necessarily moral guide.
And Carlos being more empathetic can also feel all Dresden inner darkness, even if 80% of them is Dresden's neurosis over them.

There are few options:

a) it was Hendricks and Marcone used sorcery to wipe memory of him from all the world
b) it was Hendricks and he was either mistaken or foreshadowed by intellectus as Einhernjar
c) it was some random Einhenjar on Marcone's payroll because Gard and Hendricks were took a week off to rest on Sri Lanka

That would be really traumatic.

And in BG, Harry knows what the placard does. I don't remember if BG mentions that he has studied the artifacts or researched them, but he obviously has.

Well there were 5 artifacts lying together  - so what placard is was easy to guess by educated man.
Now force of this artifact - I'm not sure if it was matter of theoretical study - or just power of Crucifixion artifacts is so strong he can just feel what it does. Just like just knew what Spear of Destiny is doing be holding in in his hands.

4.  Excepting certain powers intervening (ala red court in Mesoamerica) the population of wizards should probably be reflective of human populations, so it certainly does seem that the council is horribly western in leadership, considering that about 60% of the world population lives in Asia.  And considering the references Harry has made about their locations, etc. it seems it has probably always been European dominated, which seems wrong unless there is a similar reduction in Asian wizard populations for some reason (hunted by jade court, etc.)

White Council is quite young. 1000-1500 y.o.
Chinese wizards could have own traditions and even after joining were mostly interested into own business, just as Jade Court avoid global politics.

It's awesome, but in a way too fan-servicey (not maybe for me but I assume for most) and it's very much against how Butcher constructed Dresden character. Even his decision to empower himself at the end of BG is way more linked to his family and friends - than any righteous killing machine mode - I believe in this aspect Mab is doomed to fail (assuming that's what she really want).

From all those options I assume "drinking" is maybe though Dresden never was a drinker even in his wanna-be-noir years. Harems are quite obviously out of the question, (not to mention Lara would die, and Molly would kill Dresden if trying), just as enemies head on spikes.

First I wanted pointed few things about Columbus of all things:

Columbious wasn't trying to discover Amarica or prove that the earth was round. In fact, Columbious believed the earth was flat, and continued to believe it until the day he died.

I'm quite sure this is not true. Whole Columbus expedition was based on assumption Earth is round - but smaller and there is no Americas.
Columbus was in fact believing land he discovered was Easternmost part of India, and he died believing that. (I mean if he believed world is flat why would he he sail to India - straight West).

Amarica had already been discoverd by other exploers, most notably the Vikings and Ferdanad Majelien. Columbia's was actually trying to find a faster Trade Rout to Asia. Instead, he wound up in South Amarica.

We can say America was discovered by multiple tribes before, but when we say discovered in Columbus context we speak about perspective of let's say Eurasian civilisation. Viking settlements were earlier - but they were not known to Europe as whole.
Ferdinand Magellan was 12 when Columbus reached Carribean Islands. His discoveries - are decades later than Columbus.

-Third. When Columbis finally did land, he and his crew were greeted peacefully by the natives, who Columbis and his men began to kill and enslave, until very few of them remained. He then took, along with the slaves, all the Spices, Fabrics and Gold his ship would hold, and returned to the queen and his homeland in Victory.

That is vast oversimplification of longer process than truly in fact lead to downfall of Taino culture of Carribean Islands. (Not to absolve Spanish of their crimes, but it's simply not like Columbus came with his three ships and killed 2 million natives on multiple islands and then returned victoriously). Also reactions of various Taino tribes towards Spanish differed - there were violent reactions.

Bonus Fact: Two of Columbiouses ship, the Nina and the Pinta, are Sailor Slang for Prostituets. Being a God Fearing man, Columbious made them name the third ship the Santa Maria.

This is not really certain.
Primo, by custom all Spanish ship or almost all had Saint's name and unofficial surnames.
We know Nina (girl) was names Sainta Clara. And that her nickname was rather pun on her owner Juan Niņo surname.
Santa Maria was nicknamed "La Gallega".
Secundo, neither of those ships were Columbus property. They all had owners - mentioned Juan Nino, Cristobal Quintero (Pinta), Juan de la Cosa
(Santa Maria). So it seems not improbable they all have their names estabilished before Columbus organised his expedition.

Now in terms of Luccio's words, I see no reason to treat it as Holocaust denying - I mean considering overall stories of DF I could make guess about sligthly right-wingish libertarian believes of Butcher - maybe, but how such interpretation would even hold in overall scheme. Especially consdiering Butters character?

But I also do not think it's simply hindsight thing.
Let's remember that one of allies was Joseph Stalin. Let's remember Soviets were trying to push some of their crimes on Nazis - like for instance Katyn massacre. And you have ignoring truth about many real attrocities on the other hand. Quite a mess.
Dresden know Nazis from comic books, and films when they are just sort of bland, death-cult spooks. Luccio knew people, and she had centuries of messy muggle politics remembered. And she also knew beings that would make Hitler, Stalin, Churchill and Eisenhower to shake hands, open fire from multiple machine guns and then be shredded into many bloody pieces (which arguably would make WW2 politics maybe a bit simpler). Beings like Dracul, Shagnasty, Outsiders, Denarians... She won't go all Manichean on mortals. Not even mortals with lot of blood on their hands. I mean remember what Jim wrote about soulgazing a Hitler.

(Or maybe she's just crypto-Mussolinian in heart )

It is a bit of a cop out on Luccio's part because the WC was in a position to examine the stories of atrocities. Even though there were a lot of them, determining the truth of them all would have been possible for the council, though it certainly would have occupied a lot of time.

And then which attrocities would they stop? Hitler's? Stalin's? Japanese? Lot of places to be for organisation as small. Especially when you cannot just kill the bad guys. Especially if there are warlocks and sorcerers fighting on different sides that needs to be taken out - and necromantic death cult using World Wars for his own purposes.

Funny fact in Forest People language Genoshkwa means "War Path" but it also can be read as "Gossip Girl" - it all depends where you count this H in the middle.