Is there anything that you can do with both dogs, a short walk? Maybe someone you know can walk with you? He just doesn't understand he can hurt the other dog, right now I think that is the most important thing to work on. Getting them to live together peacefully for their safety and your sanity. Take a deep breath and look at the situation like an outsider. You will find a creative way to fix this. You have done well with this dog and I feel it sometimes gets worse before it gets better.
Misty- Samoyed Mix, Tannor- Golden Retriever CGC
Robyn- GSD CGC, TC, Midnite-GSD CGC,TC, Brennan-Golden Retriever CGC, Batman-Husky/Greyhound , Apollo-GSD