There's so much advice I would give! But I agree with both suggestions: Teach your dog to love a crate, and only train using positive reinforcement methods. No matter how difficult the training can be, whether house training, teaching him to be quiet or not to pull on leash, remember your dog only does what he knows. If you want him to behave differently, TEACH him, don't scold him.
My younger pup was very fearful and anxious. This caused her to bark at just about everything when we were out walking and she was too stressed to focus and listen to me. If I had scolded her or yanked on her leash, she would have become aggressive by now. Instead, I started very slowly, at a distance she was comfortable with, to pair yummy food with her triggers (other dogs, people, noises). Now she looks to me when she's scared, instead of barking. I went through the same thing with my older dog, to a lesser degree. Positive reinforcement works, but it does take time and patience.
This past weekend I was able to enter both dogs in a Barn Hunt competition with many other dogs and people. It was very noisy and exciting, but both my girls were calm and focused. That is simply training. Don't believe that all Doxies are yappy and dislike bigger dogs-they do tend to be that way, but if you teach them to be comfortable and to trust you to protect them, they won't feel they need to protect themselves.
Also, don't over feed your pup. They can get fat very easily and that is hard on their long backs. I recommend feeding portioned meals of a high-quality kibble or raw food.