Interesting theory! It's as valid as any other. I agree that Nika's memories, particularly in his dreams are not all they seem. At this point, "The Cabin Incident" (Nika/Summer at the cabin) and "The Violent Incident" (Nika requiring hospitalization for severe injury) are spoken about like they're two separate incidents.I'd say there's a fourth way but it kind of links into the first point and is my own crazy theory (likely full of holes) - Nika and Summer were abducted and taken to the cabin. He's suppressed or altered his own memories to some point and remembers it as walking there. Something bad happened at the cabin (Nika stabbed and left for dead/last time he saw summer/etc) and Officer Laverne headed up the rescue mission. But to Nika, he remembers it as walking there and spending time with just Summer before she 'vanishes'. To me, Nami and Noji's reactions when they refer to things like the Violent Incident or are cagey when talking about how Summer vanished.
If even a fraction of that is close to the truth, the Amber visit could be quite a brutal piece of story telling if Ocean can pull it off
The problem with any reveals during Amber therapy is that Nika already decided to bullshit Amber because (a) he was protecting Cheeto, and (b) he knows Bella reads Amber's clinical notes on his file and wants to mindfuck Bella. While Nika has apparently resolved to come clean on (a), we don't know if he will continue to BS because of (b). Added to that, we don't know exactly what BS Nika has told.