Many people seem to have different pain, my pain was mainly on the right front low so always thought it was my intestines. It mainly happened after I ate and that is the reason I did an US 6 years ago.
In the beginning I also had pain at the left like in the spleen area, never found out why, don't have it anymore.
Now when I have a pain, it feels like a general sickness with very painful shoulders and collarbones, I must say I never heard that from anyone before. High backpain is more a normal reaction to gallbladder problems.
When I even feel something slightly I drink 1 tbs Epsom Salts dissolved in water and in 15-20 minutes the pain will go away.
I have a 28mm gallstone so I do mainly flushes to avoid new stones so my stone can be happy by itself.
I did not read your link but indeed it is helpfull to eat the right diet.
Though I must say, I don't advise this to anybody, I changed to a high protein diet since I can't tolerate many carbohydrates for other reasons. I do order my meat which is from grassfed animals and chemical free from a website.
It is a choice I made and may be some day I might need gallbladder surgery but so far I am ok.
If I go overboard at dinner I sometimes have some ES as prevention. You can also use a pinch of ES in your food.
As you can see you have to find out how your body reacts, so I would start with some Epsom Salts , since there are 3 tsp in a tbs you could just try 1tsp and see if it works.
Once the 1 tbs did not work so an half hour later I took a 2nd tbs and that worked, but you have to be prepared to stay close to a bathroom and don't go out.