Are you familiar with Derek Parfait's "Repugnant Conclusion"? https://plato.stanford.edu/entries/repugnant-conclusion/

It does not necessarily hold that killing lots of dumb things is worse than killing fewer smarter things, but it could.

So with reference 2 I don't understand how you can be okay eating mussels but not okay eating eggs or dairy. If a hen naturally drops eggs and those eggs don't turn into chicks, they will rot anyway. And dairy involves no death. So why would one be "vegan" and eat oysters but not eat dairy or eggs?

Dairy and eggs both involve the death of animals. Dairy cows produce milk for their offspring. In order for us to get milk the offspring must be removed. Typically males are sold for veal, females continue as dairy cows. The production of laying hens results in roughly 50/50 male vs female chickens. Most of the males are killed shortly after hatching as they are not the variety kept for meat.