Sorry for the wait I will try to help you but you made me realize how many things I skip when I read as long as I get the overall meaning.
"Answer to Aislin
1- What’s this ~けりゃ suffix? My best guess is 蹴る.
けりゃ is the informal version of ければ
so it is : “You said you want my help so of you want it shut up while walking.”
some links: here
2- It’s the scene when the “grandma” says Chuuya’s her grandchildren’s age. I don’t understand the grammar the grandma uses here. Is it just “it would be good if I had any grandchildren, though”?
you are right. 居る means to exist. たら is a if and良かった is the past of good.The joke here is probably that she says he makes her think of her grandson(a kid probably) then had if she had one. She calld him a child and we know how Chuuya likes that.(knowing it is dazai make it fun because he know how to make Chuuya angry)
3- I don’t understand the part I marked red.
揶揄う(to make fun of)
って= informal of to say
くるう= to come
“if he knows that, many years of ridiculizing is coming.”
In short if Dazai know of this he will ridiculize him
4- Same problem as above. How does 捨てる fits here, is it an idiom?
I think it’s just the verb to throw away.
“Even my disguising technique hasn’t been thrown away right?”
“He even changes his bone structure right?”
I haven’t found any other meaning for 捨てた
5- Does Kyouka say here that she cannot use scissors for assassination?
“You can’t use scissors as a murder tool.”
Probably a joke because she is a murderer. But it’s common sense for Atushi.
You had it right
6- I don’t understand what’s happening here. Did 夜叉白雪 just also wanted to play? Or did she didn’t like something here?
In the other panel before you can see that Atsushi does not recognize what she made. She just got embarrassed at her cutting skill and destroy it all to prevent further humiliation. She his hiding her face will be destroying it.
7- I want to confirm my translation - so, Chuuya is generally calling Atsushi a crybaby and he gives him an advice to talk back to people instead of crying?
I hope that helped you. I had to search for some of them. I understand some better now thx to it. Sorry for the delay I forgot to answer yesterday.