I can't answer all your questions, but I'll tell you what I know.
First, my symptoms were very similar to yours. The only symptom you mentioned that I didn't have was the pain in the arm area. You can definitely suspect GB problem. Ultrasounds can miss, or fail to detect stones, when in fact there could be many. Epsom Salts help dialate the bile ducts, so that the stones are flushed out easily, and so you'll have the most volume of stones expelled possible. Other methods can be successful...those that don't use epsom, however, I'm only familiar with the cleanse that uses epsom.