You are correct about lettuce and avocado - and I like the idea of avocado and will try it. But sadly, tomatoes are probably the food that gives me the worst heartburn. My favorite way to eat hamburgers was with tomato, lettuce and mayo and I could've lived on BLT 's. The joys of getting older!
I should have realized that the acid in tomatoes would upset your digestion. The are very few foods that have an adverse effect on me. I finally threw out the tube of Tums I had when I noticed they had expired in 2019!