Do you think they would meet again once Joel abandons Clem in Montauk?
This is probably a minor and mute point, but I am unconvinced that Joel and Clem would have continued a relationship after the first time they meet.
As I understand the timelines, the last of Joel's memory of Clem that was erased was the very first time that they met: Joel was taken to the beach with Rob and Carrie; Clem approached Joel and they spent the entire day and evening together, up to the point that Joel was humiliated in the abandoned house and fled from her; during the car trip back home Joel replied to Carrie's question about Clem with "she was, uh, just a girl". That sequence of Joel's memories were the last ones that Stan and Howard erase. This is confirmed by Clem's hair colour, since it was on that day, and only that day, that Clem had her hair dyed green.
What I don't understand is how Joel and Clem went forward from there, to their first dates together in the forest, when Clem had her hair dyed red. I understand it is speculative, since it is not told within the story, and a mute point since obviously they did, but I don't really believe there being a likely scenario given their personalities. Sure, they could have exchanged phone numbers earlier on the beach, or met again at the bookshop...but Joel's personality doesn't seem too resilient after such a humiliation, and his "just a girl" statement seems very final. Would he have had the courage to pick up the phone? Or would Clem have gone searching for Joel the next day after he abandoned her at the house? She is one that is "just a *beep* up girl, searching for her own peace of mind" and refuses to allow someone else to assign that responsibility to her. Would it really be likely that she would go against her own belief and pursue a man that abandons her? The story Clem later tells of her childhood about the ugly doll, "don't be ugly, you can't be ugly", that concludes with her plead "Joely, don't ever leave me", would suggest she is unlikely to take on that responsibility for someone who has just rejected her.
The second time they meet at Montauk has a progression that is more consistent and detailed, and because of that, the two separate events of Montauk blend into each other and give additional credibility. However, if the first time is teased away from the events of the second, I believe it makes the start of their relationship unlikely.