As a general statement on forum use, the only thing to be mindful of is that if you are replying to multiple people at at once, it’s better to reply to all in one post, rather than doing a separate post to reply to each. This is done by selecting the text from a post you want to reply to, then select “quote” from the pop-up that appears. Doing this, you can quote+reply to multiple people in a single comment.
Aside from that, sometimes, you’ll post something. Then later you’ll want to post something else. But no one else has posted since you last did, so now you end up making two post in a row. This is okay as well.
Your interpretation is completely correct. The これ refers to 化け物 just as you suggest.
For the dialogue here, says the すごい line, and says the “no time for” line. Viewed this way, does the dialogue make more sense? If not, I can definitely go over it.
Correct.
From a grammar standpoint, there’s a nuance that Yui knows something (what she wants to do about it), and Kotoha doesn’t know that something (what Yui wants to do), so when she asks, the の changes the sentence from “(We) kill (it)” to “(It is that) (we) kill (it)”. However, it’s clear to a Japanese person that this is spoken with rising intonation (a question, rather than a statement), for “(Is it that) (we) kill (it)?”
Correct.
For this translation, I’d place the stammer on the “We”. The stammer isn’t on a specific word so much as it’s at the start of the response. (I think an argument can be made for the way you wrote it, though, so take my words here with a grain of salt!)
Going with your translation as a basis, I’d change it as “But this kind of monster needs to be violently killed.”
I went for “this kind of” as a translation for こんな (where “this” would be この). For べき I favored “needs to be”, but I’ll admit that when I see this used when reading, I don’t think out how it may be conveyed in English, so this may not be the best way to word it.
My own translation would probably be, “But a monster like this needs to be beaten to death.”
I think that does capture it most precisely. Naturally when translating into English you’d want to consider what overall sounds best in English, but “that said” is always my mental starting point when translating a だって-starting sentence into Enlgish.