Dear Kimberly A.,
I am not familiar with the sort of camps you mention. Perhaps one of the readers of this Forum will know more than I about this.
Children who have difficulty with anger face a number of challenges. They need to 'figure out' why they become angry - i.e., what circumstances precipitate their angry response. They also need to figure out how their anger gets in their way, and what sorts of alternatives they can employ.
You have decided that your son's problems with anger are directly related to the circumstances associated with his father. You may be correct about this. But often, particularly with young children, the matter is more complicated.
Cognitive-behavioral approaches to problems with anger tend to be effective. Don't give up on your son's therapy. He may also benefit from a group therapy approach. Check out the options in your area.