Why the heck is Han Myungoh looking cool here?!

I think it was to spread the name? Like how he did before. Tho I don't think this really explains why (￣∇￣")

That's a bit confusing.. So, let me get this straight..
1. He couldn't use his own name because it'd alert the star stream, so he used YJH's.
2. He stole the revolutionary title to get back into the scenario and survive.

So... How does the disguise work in his favor when people (citizens, characters, demons) have already seen his face? Who is he trying to deceive?

I think you forgot that the people can’t really see his face because his face is blurred because of the forth wall and thats why the woman (i forgot her name), the one who fixed KDJ, said to him „why is your face blurry ?“ (⌒▽⌒)
I think there was also a chapter where one of the girls in KDJ group ( i know im bad at memorizing the names) was confused why they called him Ugly and why they can’t remember his face. But thats all thanks to our great forth wall who is keeping KDJ beauty to himself and of course we keep his beauty to ourself. (づ￣ ³￣)づ.
And about the last question it could be that he doesn’t know that they can‘t see his face clearly and thats why he's trying to change his face so that they wouldn’t recognize him or that they would believe him that he is YJ

I hope that this helps you (☆▽☆)

Yeah, I know his face is blurred. He doesn't know his face is blurred.
My point is that I thought when he declared himself as the revolutionary his face was already revealed to those around him (the citizens and executioners included). So why would he disguise himself when he doesn't plan to hide? (It'd be another case if they didn't really notice his face.) Aileen also said that he doesn't look much different after putting it on.. (￣∇￣")
Does he just wanna come off as charismatic? Does it have the type of skill that would compel people?

I think that's something we'll find out in the next chapter....