What is the actual English spelling for "Kono Oto Tomare!"?
The Romanized form would be Kono Oto Tomare!  What you see is correct.

The Japanese language does not require that sentences contain spaces except if the sentence comprises only of Hiragana and Katakana, which at that point it becomes optional for clarity or to disambiguate what's being said.

The likely explanation as to why it's stylized in that way is for stylistic purposes, or to give an indication as to what each individual character was in terms of pronunciation.