I feel for you as these attacks can be pretty painful. Diverticulitis occurs when diverticular pouches, that at least half the population get as we age, become infected/clogged with bacteria leading to inflammation and likely gas in the pouches. SIBO is sometimes involved as well. The good news is that SIBO bacteria as well as bacteria within diverticuli feed on carbohydrates. Therefore the Fast Tract Diet should prove helpful by limiting the fuel these bacteria consume.
Some of the foods you mention (seeds for instance) have been debunked as triggers for diverticulitis. You might make a list of the foods you are unsure of and consume them in moderation until symptoms improve, then introduce them in a controlled way. Please keep us posted on your progress.