Gastritis Support Group
Gastritis is a medical term for inflammation of the lining of the stomach. It means that white blood cells move into the wall of the stomach as a response to some type of injury. Gastritis has many underlying causes, from infection with the bacterium H. pylori, bile reflux, or excessive consumption of alcohol or certain foods or drugs like aspirin.

Nuts are hard to digest. I'm not sure about the fat issue. You could try soaking them overnight as this helps them to be more easily digested. These nuts would need to be refrigerated then. I'm ok with most nuts just in small amounts. I haven't tried peanuts as they are the worst offenders.
I hate that you think you're getting somewhere with all of this and then wham...you've slipped back and didn't notice.
Like me you have more than the gastritis to manage and that makes it hard to juggle foods doesn't it?