Thank you for taking him in!
I agree with LBJ, he’s been living outside, fending for himself in a world that’s full of dangers. Almost all bigger animals wants to eat a rabbit, they’re near the bottom of the food-chain. They have to be tough to survive, even tougher than wild rabbits that live in colonies that offer protection and safety in numbers.
One of my bunnies was living outside when I found him, and he charged at me for quite a while before we became really good friends (he’s sitting under my foot as I’m writing, because he loves being pet). He even bit me. He pummeled me and growled and the next second, he demanded pets by putting his chin on the ground. He can still growl, but he doesn’t charge or bite now (exept the broom, the broom is his sworn enemy). He’s a smart, curious and feisty bunny and those qualities were probably what kept him alive outside.
Cage aggression or territoral defense is common in rabbits. They are territorial as a species, because they live in warrens outside and invest a lot of time and energy in creating these intricate warrens, they can’t just migrate away if there are intruders that want their space. So they stand their ground, and it’s surprising how belligerent such a crazy cute little animal can be.
Some of it goes away with neutering, because territoriality is sexually motivated to an extent. The rest of it has to be dealt with by gaining the bun’s trust. They are very different from dogs and won’t respond well to punishment – in part because they’ve been domesticated for a very short time compared to dogs. Try and put his food-bowl down in a place where he isn’t, food aggression means he isn’t sure he’ll get to keep the desired food unless he fights for it. He will most likely find his bowl wherever you put it, because he’s had to find food for himself and rabbits have a very keen sense of smell.
It is problematic that he’s bit your wife, but it’s not like if a dog bites a person. Biting should be bred out of companion dogs, but bunnies were never, until quite recently, bred for their capacities as companion-animals. I probably sound silly but I’d wear long (old) trousers and try to stand my ground (if he succeed in chasing you away, which is his intention, he’ll repeat the behavior). A bunny’s bite is not as bad as the bite of a cat or a dog, since rabbits are vegan, they don’t have the same nasty bacteria in their mouths as especially cats have. They can bite really hard though, so don’t try to fend him off with your hands unless you’re wearing gardening-gloves.
I sincerely wish you all the best with this, and we’d be really happy for updates. We have had cases of badly aggressive bunnies here before.
Here is an informative article from the House Bunny Society, not all of the info in the article will apply to your case of course, but it might still be useful: aggression rabbits