SFX explanations are all over the place. If you can read Katakana you can easily search the onomatopoeia meanings on the web/ChatGPT.
pg.8
Panel 1 is a blood splashing sound effect (Do-shu, like blood splattered to a wall)
Panel 2 is him snapping his eyes open (Pa-chi)
Bottom middle panel is him putting food in his mouth (paku-paku)
pg.17 bottom panel: "zushi" conveys sluggishness due to weight
Pg.19 "gakun" is an abrupt heaviness/stopping