Painted Doll is the offspring of the Devil and the White Queen
Explains her hands movement and apparent high standing among the Carnies.
The Twin leads Tamara to discover The Scorpion with Painted Doll
When Tamara sees The Scorpion outside the tent, he just happens to be standing in the same spot (and with the same body position) as The Twin was during his "Lashes lashes, we all fall down" line. He doesn't actually speak to her, and upon vanishing into the tent, manages to find a scarf and start making out with Painted Doll in the time it takes Tamara to round a corner and walk a few dozen feet. While the carnies are assigned specific sinners, they certainly seem to "help" where they can (Wick and the Woe Maidens tormenting John, Doll giving him information about his son). It stands to reason that The Twin was luring Tamara into the tent so that she could catch The Scorpion, giving her ample reason NOT to trust him (and thus more effectively damning herself when she ignores the warning signs yet again).
The Ticket Keeper is Raziel
Out of everyone in Hell, The Ticket Keeper is the only one who seems upset by the situation. He is visibly shaken by the lashing The Tamer gives Merrywood, seems to honestly pity John (going so far as to both give him advice AND wave off The Tamer after John breaks one of the rules), and generally comes across as more of a caring father than supervisor. In some versions of the story, the angel Raziel is cast out of heaven for the sin of giving man knowledge (often knowing in advance that his actions will result in being cast out). As a result, he remains benevolent to humans despite being a fallen angel. The Ticket Keeper is in charge of informing the sinners of the rules (knowledge), appears to hope all of them will see the error of their ways (loves mankind enough to go against God), and seems to be on relatively equal terms with Lucifer (having been either equals or close to it in Heaven).
Tamara was sexually abused by her father
For one thing, it fits with her pattern of seeking out destructive relationships, a common thing for victims of rape and sexual abuse to do. Then there's the song "In All My Dreams I Drown." A sad, haunting lullaby with strong themes of powerlessness, (likely non consensual) sex, fear and dependence.
In the song, Tamara begs the "captain" (Lucifer) "don't make me go to sleep." He responds with gentle authority ("Hush, now, hush, love / Here's your gown / There's the bed / Lanterns down") very much like a parent enforcing a bedtime. But his paternal tone is mixed with images of him pressing her into the bed in an unmistakably sexual manner. The song's lyrics reinforce the idea of rape, and of Tamara's powerlessness. (The captain howled / Heave-ho, heave-ho / And tied me up with sheets) (Captain, Captain! / I will do your chores / I will warm your cot at night / And mop your cabin floors / Scold me, hold me! / I'll be yours to keep)
Tamara's fear of sleep and bedtime exists because that was when her father would sneak into her room to abuse her. The feeling of drowning and being pulled down into hell represents her pain, her loss of control over her own body, and the loss of her innocence. The nautical theme comes from a bedtime story she was often read as a child that her traumatized mind chose to view the rape through, to protect herself from the pain.
Hell works on the karma system of Hinduism and Buddhism
John is released from Hell because he manages to accept his grief and determine to continue with his search for his son despite his loss of hope.
Tamara and Merryweather, on the other hand, end up trapped, not because of any actual sinfulness, but because they're unable or unwilling to learn from their past mistakes. The song "In All My Dreams I Drown" is actually Lucifer trying to help Tamara confront and come to terms with her father's abuse so she can break out of her cycle of abusive relationships and earn redemption.
Lucifer actually looks like a normal human.
When we first see him, he's sitting at a makeup table. While it's fairly obvious that the black-and-white KISS makeup is artificial, there's no reason to think the red skin, claws and horns are any more real. After all, the Carnival includes many performers who look just like normal humans but for their makeup.
TDC was written in the Repo! verse, as a satirical anti-Genetic Opera
God explicitly looks like Rotti Largo because of the religious air he's given and evil because he's really more of a mob boss than a savior. Hell is a representation of life on the streets and the carnies are the more dangerous and vindictive outlaws. It ends with the people wanting to rebel against an unfair system led by an uncaring tyrant, the people want a Revolution against something like, oh, I don't know, getting the organs ripped out or being put through hell in other ways. Who wrote it? Graverobber of course! After all, it must be boring being poetic and understanding of absolutely everything just to point out the obvious.
The Magician isn't quite as inept as he seems.
Considering how little screentime he got in the first chapter, much of his character is still up to interpretation at this point. Maybe once he finally gets his time in the spotlight, it'll be a Beware the Silly Ones
sort of moment?
All the Carnies are the souls of the dead forced to work for Lucifer.
It's possible that when the Carnies died, they became slaves to Lucifer and their behaviours and appearances reflect what they did to end up in Hell in the first place, which could also be reflected in their songs and their positions within the Carnival. For example, The Twin could have been a conman who took on several guises and identities to trick his victims. Wick and the Woe-Maidens could have been tricksters in life and one of their greatest tricks was to release bees from the church (Here is the hive/Where are the bees?/Buzzing around/ Where no one sees/Here is the church/Over the steeple/Ready or not/Sting all the people!). The Painted Doll could have been a bitter woman who poisoned her love, hence her 'Cup of her Scorn'.
- Alternative guess on Wick and the Woe-Maidens: They tended to lure people in via their sexual wiles (Don't you wanna/kiss the girls!), quite possibly including members of the clergy. Why bees? Why, it's a Honey Trap.
- Or maybe the Twin literally wore other peoples' faces over his own.
Tamara is stuck in purgatory now
Tamara screws up trying to get out Hell due to her flaw (guiliability), but since she wasn't that bad of a person, Satatn gives her a sort of second chance. This is why 'In My Dreams I Drown' takes place during the credits.