According to the latest research there is no solid evidence that UC can be treated by diet. On the other hand some people have had success with diet modification. I would continue in your current treatment Humira + 5ASA + low residuum diet. After several months you can try SCD, AID or diet diary. But do not expect too much from diet modifications.
Actually there is one recent study which shows SCD alone can induce remission. There are a handful of other documented cases of diet alone inducing remission.
Not a large study, but promising none the less. Thirty years ago if you told a gastroenterologist that a bacteria was responsible for the majority of stomach ulcers they would have laughed in your face. IBD is a complex disease with multiple causative factors. Genetics, stress/environment, diet, and bacteria all play a part.
There are some very intelligent and ahead of the curve gastroenterologists out there, they are just few and far between. These are people exploring diet modification, fecal transplant, etc. Good luck getting an appointment with one of them, however.