I’m not sure if this will help, but I think the reason a Symptom can also be considered a side effect is because it’s always somehow motivated or influence by the Problem, i.e. a side effect of the Problem. So it’s really the author’s perspective that calls it symptom & side effect – you as the author know there is a real problem out there that’s the real source of trouble, and you know that the characters are only dealing with the symptom, as a side effect of the actual problem.
Have you seen this? Causes and Side-Effects in the Main Character
When encoding the Symptom & Response, I like to picture in my head the quad sort of turned slightly, into a diamond shape, with the Problem hanging over everything, causing all the trouble like a dark cloud. In its shadow the Symptom & Response work, while hiding under the ground waiting to be unearthed lies the Solution, like buried treasure. Like this, where Oppose is Problem and Hinder is Symptom:
As far as Speculation and Projection go, I’m not that familiar with those elements … I think in actual practice it will be a bit between your two ideas. Like Joe might see his Mom wasting all her time speculating what will happen if she calls Joe’s sister, whom she hasn’t spoken to in years. And Joe is just like “Look Mom, just call her. It will turn out okay, you’ll see. She’s never held a grudge before…” Meanwhile Annie (some other OS character) might get all upset when she sees her own doom in her tea leaves, and responds by trying to anticipate or figure out exactly how that doom will play out.