> Simple teleology defeats it, in the sense that everyone who holds this view will probably die childless, and will not be very successful at spreading their views generationally.
This is very silly, it plainly conflates truth and popularity.
> As for the animals - hey, I said I want them treated decently.
Suggests "decent" treatment of animals is preferable to "indecent" treatment; this is broadly accepted.
> I don't extend them the same courtesies as I extend to humans because they're not human
Suggests animals/animal suffering are/is of less moral importance than humans/human suffering. This is also broadly accepted.
> I don't shed a tear for their deaths because to do so is to anthropomorphize them, a quintessentially childish way of viewing the world.
Suggests anthropomorphisation of animals is undesirable because it is stereotypically childish; childishness is bad. Seems like quite a silly argument, kids are also fond of breathing etc.
> Said animal wouldn't exist otherwise, and could not benefit from not existing, so the potential for benefit is always higher on the existence side, even if the probability is very low - it's still higher than a guaranteed 0.
You care about the expectation, not the "potential for benefit".
In any case, the way in which you've presented these ideas suggests that you're a consequentialist maximiser (eg think that it's the outcomes of actions/choices/rules that matter, and that there exists some partial order of the desirability of possible worlds). I'd suggest that if you keep thinking about animal welfare and how to balance the lives and living conditions of animals against your own social and dietary needs, you may well decide that you want to reduce your meat intake. Peter Singer's "Animal Liberation" is fairly classic, "The Possibility of an Ongoing Moral Catastrophe
"[0] is much more general but pretty great.
[0] https://link.springer.com/article/10.1007/s10677-015-9567-7