I should probably point out that the monsters named so far aren't an exhaustive list of all the ones on the planet, but just a list of the sapient ones. The less intelligent monsters with no humanoid sapience don't organize themselves into anything so advanced, and are mentally incapable of joining the Zodiac Tribes. So there's probably lots of monsters out there he could cook and eat without worrying too much. It's like you said, if it can ask you to stop, you probably shouldn't eat it.

If you choose to go the goblin route, be an Uruk. They're one of the biggest and most dominant groups of the Cancer Tribe, and I've got some fun stories charted out for them.