Hello, thanks for your question today! I am Dr. Drew, and I am a licensed veterinarian. I'll be happy to help you in any way I can.
Given the situation you described, with failure of alternative therapies such as the pheromone collars and homeopathic remedies, I'd suggest something more mainstream and proven.
Behavioral medicines such as Clomipramine or Fluoxetine can be given daily, with generally good effectiveness for reducing obsessive-compulsive issues, which include separation anxiety.
These medicines are generally very well tolerated (safe for long term usage) in dogs.
They are available by prescription only, but are not particularly expensive.
I'd suggest one of those as the next step for Rodney.