I'm generally enjoying this, but everyone going "But..How!?" whenever he actually remembers something stands out so much.
They're all so shocked that he remembers stuff they so desperately want him to.
I assume the intention is to play out the idea that they've gotten used to the idea of him not having any memories, and having to basically relearn things from scratch, so every time he suddenly blurts out something he's remembered (as opposed to something he's been told) it surprises them, and they're happy because it means he
is getting things back.
So it's sort of a combination of being a bit emotional, and a mix of hope and trying to manage their expectations/fears. They want to believe that he's remembering things, but on some level they're afraid that someone else might just have told him that, so they feel the need to kind of confirm everything. But they also don't want to get too carried away, because just getting back little fragments of memory doesn't mean it's all coming back.
So they're kind of walking around on eggshells a bit around him, because they're not sure what effect their actions are going to have on his recovery.
Also, selective amnesia is fun. Forgets that he was screwing his sister-in-law and looking to screw his sister, but remembers that cheating is a no-go and incest is icky. For someone who goes with his feelings, this hangup on societal norms (that he shouldn't remember) is weird because he should've instant "felt" that it was the right way to think things.
This.
Though it also ties into the "I want you to remember X but I'm not going to tell you X" problem. Why would all of these people be hesitant to tell him what he was doing if they already know he was completely cool with it first time around? They should generally assume that if he was fine with it then, he should theoretically be fine with it now (especially since the current version of him
should have even less societal hangups about things because he shouldn't remember what society thinks is right or wrong).