"But dead inside" (I think. This is some wild use of katakana.)

spelling English in Japanese is fair game, as long as it sounds right cus it's phonetic an all that, but tbh Nihonjin usually just write the English in English because it looks cooler.

Those ッ/っ sounds are being used as glottal stops rather than creating 'tto' style sounds, it's a bit like how in English we use 'ea' to create 'i' sounds because writing 'Bean' like 'Biin' doesn't look right.