My heart goes out to you. I have had a few horrible dumping episodes. They were enough to make me wish that I had the VSG instead of the RNY. (I didn't know that people could dump after the VSG - oh dear.)
Artificial sweetners don't cause dumping but excess sugar and fat do. My worst episode was after consuming too much of an oily salad dressing. It sent me into a full blown panic attack due to the extreme discomfort and then I was hurting for two days afterwards.
In time, I've learned what I can tolerate and what I cannot. Once in a while though, something can still surprise me by not digesting well. I agree with the comments above. The safest thing to do with a new food, is to try it at home first, when you have a bathroom handy.