Tom, I think it might be a good idea for you to start a food journal wherein you write everything you're eating and the associated effects: headaches, cramping, diarrhea, gas, bloating, numer of bms etc...and I think you'll be able to find some correlations specific to what YOUR gut can and cannot handle.
Just remember that transit time is very different i.e. in some people symptoms present within a few hours, in others it make take a few days.
Yes, the SCD is rigorous, but for many of us it really works.
And then when you add to it some natural supplements like L-Glutamine for colonic repair, slippery elm powder (IMO a substitute for the mesalamines), and probiotics like VSL #3, you can get exponential results.
Be careful with whey protein and whey isolates, many of them are loaded with sugars and other junk, which won't be good for your UC.
The only whey protein I can recommend because I use it myself without any problems is: Dr. Mercola's Pro-Optimal Whey Protein. His product is from grass fed cows who are hormone free and antibiotic free, and it already contains digestive enzymes in it - which makes it so easy on the stomach. But I have to warn you, his pro-optimal whey is expensive, but worth it IMO. I have at least 2 of these shakes a day, you can see from my sig what I add to it.
Do you have a local COSTCO? I think they have a box of three almond milk at a great price.
Are you on any probiotics?