That's the first time I ever heard of a dog liking his coat so much that he growls when you try to remove it! Too funny!
Congrats on your design, but sorry you're not happy with it (even though the dog seems to be thrilled). Perhaps you could just hold him down and knit some more while he's wearing it!
On the other hand, I'm not so sure making another one for him is a good idea 'cause once you get it on, you may never get it off again!