Hello again, and thank you for your reply and helpful, additional information.
I'm glad to hear that your cat is eating, drinking normally.
It's possible that because you are away for many hours of the day, he's lonely and feels that 'negative attention' is better than no attention, so he 'provokes' you by being aggressive. Try to give him lots of cuddle and play time when you're home, and see if this biting/scratching lessens. I do think that he could be smelling the dog on your clothes, shoes, and this is stressing him out. Make sure to wash your hands thoroughly and change your clothes after walking the dog, so the scent is minimized.
I also think your cat might benefit from a cat appeasing pheromone called Feliway/Comfort Zone for Cats, which comes in both a spray and plug-in diffuser. It's available at major pet supply stores, and also online. The diffuser resembles a plug-in air freshener, but has no scent to humans. Feliway helps to relax stressed or anxious cats, and is useful in a multitude of situations. For more information, please see: www.catfaeries.com/feliway.html
In the future, when he does this, leave the room and ignore your cat for a few minutes. If you're consistent and do this every time he is aggressive, he'll learn that he won't have your attention or company when he acts like this.
Some medical conditions can cause sudden aggression, like hyperthyroidism, so a vet's evaluation and blood work, ASAP, would be a good idea.
I hope things improve, soon.