I said we haven't attempted to bring in another pet, but I forgot about a brief experiment we attempted. A lady from our church had to rehouse one of her dogs, and we volunteered to take him in to see if it would work. Our dog is small (she's some sort of papillon/pomeranian mix, we think), and her dog was a retriever.
Well, her dog tried to eat out of our dog's bowl, which caused our dog to bark at him, and he snapped at her. It was a pretty scary moment for me, but thankfully he didn't hurt her. After that, we kinda knew it wasn't gonna work.
https://imgur.com/WqDcNNq
https://imgur.com/89Z5jrB