Jon,
I don't know if this will help you, but when I was first diagnosed and was having trouble with foods, the doctor told me to start off with bananas, rice, applesauce, and toast only. He called it the BRAT diet. I was hoping he wasn't referring to how cranky I was
. He told me to add one thing at a time slowly. I was told to avoid anything with citrus, acidic, spaghetti sauce, chocolate, and coffee particularly.
It took a while, but I was able to find a few things to eat to add to my list. Eating the bananas helped me quite a bit as they seem to settle my stomach. I've had a couple people tell me it was because of the potassium, but I'm not sure if that's correct.
I did some times throw up while I was first getting my diet settled. I did not go off as much as it sounds like you are. I just wanted to share that method of adding food in case it is helpful for you. Each person seems to be a little different as to what they can tolerate. I have IBS with diarrhea and my daughter has IBS with constipation. She can eat Citrus foods at will, and I only eat citrus if I really want to spend a few hours in the bathroom. Some foods I can only eat after a good meal so that there is something else in there. For instance, if I want to have a glass of wine, I have to order it with the meal and make sure that I don't start it until after I have had some food.
I wish you luck working through this. I still remember how frustrating this was when I first had to find out my tolerances 16 years ago. I still get forgetful today to convince myself that I can eat some things that I should not. I hope some of this information can help you.