Yep I've tried feeding him both 1mm pellets and veggie flakes, he/she wont take them. I hope it makes it through the night but not looking good. If by chance he/she does make it and gets back to good health, I'll offer it for free to good home here because I don't want to see him get beat up again in my tanks.
Yellow labs are very docile, and at the same time, very resilient. but they can not take constant abuse, and him being a lone lab, makes him more of a target I think.
Did you get it from someone, or an LFS? can they take it back, if it survives?
If I lived close to you, I would take him as is. I got lots of empty tanks.
Anyway, good luck.