Protective behaviour?

I have a 40ish yr old red lored I adopted about a year and a half ago. He's been amazing with us, bonded very quickly with myself and my husband, super gentle, no bites and allows lots of scratches. He didn't come from a great place and only whistles and eats his peanuts. I don't care, I just want to give him a nice home to live out his days.
7 months ago we got a dog. And his behavior immediately changed. Since then he's been very aggressive and has bitten us several times, drawing blood. We Didnt think it would be an issue as he whistles at every dog that walks by the house and at the time we also had a small dog that he didn't have issues with. Since then the small dog has been rehomed with my sister and we're down to Molly, our pit mix. We've been giving him space and talking to him but it's been the same.
Tonight, he was waking around on the floor with Molly, not attacking her at all. But when my husband starting petting her, Clyde (bird) tried to attack him several times. Leading us to believe that maybe he's being protective of the dog? And if so, it's been 7 months now. What the heck do we do?

You will not like the answer, but it is what it is! The dog needs to be rehomed. Yup, knew that you wouldn't like that answer.

Can you create a world that Parrot and Dog can live in? Yes, its possible - but will require starting from the ground-up! If you are interested, there are methods, but it will require time and a deep interest in making it happen on the Human side of all of this!

Protection is part of it and from several different vantage points.

He loves the dog, that's my point. He's attacking us.

It is tempting to interpret an animal's intentions as if they were people, but this is often misleading. Parrots, especially, are not domesticated and while they are like us in many ways they also differ in important ways. I speculate that the bird does not like the dog, and is not so much attacking you guys as trying to drive you away from the danger. "What's the matter with you, can't you see that dangerous thing? Fly, fly!" But even that is a conjecture.

What is not debatable is the risk to your parrot of living with a dog. For one thing, a dog has instincts that may lie quiescent for many years. Then one day the bird does something that triggers an instinct and the dog snaps at the bird. The bird might be killed outright, but even the dog's saliva is dangerous - it contains bacteria that birds have no defense against. I've read posts from users who had dogs and birds coexisting for years, then one day the dog just snapped. Could be age, dementia, instinct, anything.

Parrots live much longer than dogs and it's harder on them to be re-homed. Dogs are geared to people and will form loving bonds to just about any human. Parrots are pair-bonding animals who identify very strongly with their flocks, and change is hard for them. They can take years to adapt to a new home, even with the best treatment.

Accepting guardianship of a parrot is a lifetime commitment. They live a very long time, and suffer greatly if neglected, bored, abandoned, you know the drill. The parrot would probably say hey man, I was here first, you promised we'd be together forever.

First, Keep the Amazon off the floor!

When the dog is not in the house, what kind of action or reaction does the Amazon exhibit?

Has this built with time or was the change very rapid, like the same day or a day or two?

Who provides the food and water, take care of the cage, etc....?

Is there any differences whether the Parrot is on the floor or not? On the cage or not?

It is always very risky having different animals and birds. I have 4 cats and 4 dogs as well as the 3 parrots and the parrots have to have their own room with a picture window so they can still see us and feel a part of the family and have their own safe environment. I have just heard so many horror stories of what could happen and from my own personal experience with close calls just don't like to risk it. I also would suggest if you feel comfortable with it, that if you are going to have different animals don't clip your birds wings. That was a suggestion from our avian vet and it gives the birds such independence so when they are out of their room and they feel bothered they can leave us and fly back to their own space. I don't allow any ground time outside of their room because I don't want them to get attacked in any way either. Maybe he is attacking you guys because he feels less important now that the dog has arrived?