I've been suffering from these blasted things for 18 years, and have similarly noted the same sorts of correlations. My best efforts: cutting out gum; cutting out sharp foods; cutting out acidic foods; taking vitamins B-12 and C, L-lysine, and zinc; switching toothpastes and brushing techniques. I regret not recording my history of occurrences, but I perceive things are improving. At the very least, it's safe to say the cause of canker sores is multi-factorial.
Sorry, I'm rambling. No one in my life can relate, so I'll take any chance to talk about it.
You reminded me: I switched years ago to SLS-free toothpaste (Biotene), because that's supposed to help. And for many reasons, I now eat way less sugar and sugary drinks. Maybe because of those changes, or just age, I get canker sores much less frequently. When I was younger, it was maybe 2-3 times a year, and sometimes 2 at once. Now I go a year or two between single, smaller ulcers. Good luck!
I can relate. You're probably right about them being multi-factorial, but changing toothpaste has been the biggest help to me. I use baking soda most of the time and have avoided these sores for years.
I've noticed the same causes and correlation. Canker sores' formal name is aphthous stomatitis. But whether it is an autoimmune disease is debatable. As noted in [1]:
"Despite this preferred theory of immuno-dysregulation held by most researchers,[7] aphthous stomatitis behaves dissimilarly to autoimmune diseases in many regards. "
http://www.healthline.com/health/canker-sores
I've noted a correlation with: stress or lack of sleep; candy binges; eating scratchy foods like say popcorn.