Hi Joanne!
I had a Fox Terrier castrated once as he was starting to become aggressive and a bit of a handful. He was a young rescue dog and he slowly got more of a handful as he got older. He would suddenly bolt off too. The vet explained it was high testosterone levels and she recommended castration to calm him down. I never had trouble with any other dog - just him.
Being a red-blooded male etc. I had to think long and hard about that! However, he ran off again one day and the police brought him back, so we decided it had to be done. Poor old Popeye came back very sore and sorry for himself. But once his scar had healed - he was no different! We really felt guilty for doing that to him!
Over the next few weeks though, he gradually calmed down and he eventually became a wonderful dog for the rest of his life. I think if you wait for a few more weeks your dog will probably calm down too. I've only had to do that with one dog though, so that is my only experience. I recognise what you are saying Joanne and I think if you stay patient for a while then your dog will be fine.