That was amazing, and amazingly told. It really put all other chapters into context and I think makes them better in retrospect. This was the first time I couldn’t put the book down–had to read the chapter in one sitting.
You got the gist, I’d say. I’ll attempt a breakdown:
Sentences breakdown
「犬が死んだくらいで、- now that the dog is dead
帰んなくちゃだもんな。- he must return home (with complaining nuance)
何だかんだ言っても、- no matter what anyone says
みんなまだ19やそこらなんだ、- everybody is still 19 or something,
要するに子供の夏休みだな」 - in a word, it’s a child’s summer holiday.
誰に言うともなくつぶやいたその言葉は、- these murmured words that were not directed to anybody
それでも - nevertheless
このところ私が漠然と考えていたことを - my vague thoughts
きちんと紡いでいた - properly wrapped up
ので、私は、- and therefore, I [said]
I took one or two liberties with this to make it sound somewhat more understandable in English If you have further questions, I’ll see what I can do!
Oh and of course corrections from others are welcome
For the bit you quoted, this is 何も - Jisho.org#2 (have a look at the fine print) - maybe that helps you already?
But… I somehow can’t match your question to my understanding, sorry Therefore I’ll run you through the dialogue for a bit:
Dialogue
Maria says: 結構すごい冒険ね - That was quite the adventure. (Context: Tugumi took the replacement dog to the snack bar to tease the others.)
Tugumi: Yes, I even got a fever.
Tugumi laughs.
Tugumi continues: When we were children, I have a feeling that we felt such danger basically every day though! I guess I degraded. (i.e. my condition got worse)
Maria: Degradation and all, your body is weak, therefore please don’t think of [doing] things at the level of a test of courage.
At least that’s what I understand Does this help you in any way though?
Thanks, that makes more sense. I think I thought Tugumi was talking about actual adventures, sneaking around, like the post-box thing, rather than the excitement of adventure you feel as children. Which I guess maybe she was. I didn’t get the “test of courage” bit very well.
I continued reading just now for another few pages, but think I need to break now as I’m diving again tomorrow (and sharing a room so need to turn light off!). Bad place to have to stop!
Home Thread
Do you think there might be a connection? 
. I’m sure it’s just a weird coincidence. 
Does this help you in any way though?