Animals have experience? Short answer: Yes

Perhaps I'm not thinking this through or I'm simply being unambitious but I don't view effective altruism as asking you to take responsibility for the whole world. I certainly don't feel an enormous weight on my shoulders. I view it more as taking responsibility for the difference between what you would ordinarily do and what you could do if you maximised your impact, which does admittedly require consideration of the whole world.

If valid, maybe that can make effective altruism a little more palatable.

I would like to offer advice about your approach. Please seriously consider the opposing position. Consider steel manning. Do some reading about vegans and why they live as they do. Find and talk to some well educated vegans too.

There is a total of one paragraph giving passing mentions of several relatively insignificant reasons to be vegan and yet you dedicate entire paragraphs to each of "I can't supplement", "I might have to waste time talking about my diet" and "Meat tastes good." This doesn't give me the impression that you want to discover which of two possible future states are superior.

So again, deeply consider the best available versions of living as an omnivore and a vegan and choose between the two.

Disclaimer: I am a vegan, though I think this advice is debate and position neutral.