OK, here's how I see it. The flashback with Kylo is a flashback sequence. Luke and R2 is after that, and before he decides to go into self imposed exile from everyone. (Kind of mirrors Kenobi and Yoda's decision to go into hiding after ROTS.) I don't think he will be present at the time of Kylo's flashback. Him being shrouded is going to make Rey want to find out who it is, and how she is connected to that person who we know/assume to be Luke. Think something along the lines of this dialogue-wise: "While the Master was away, tragedy befell the students. The Master returned and gave final farewell to his students, before going into seclusion."
Maz will narrate the sequence of events of Kylo's attack, and Luke deciding to leave afterwards. (Mirrors Kenobi's story in ANH to a degree, though perhaps without being a Force user. Kenobi told Luke of his father but -thanks to Lucas- lied to Luke about his true lineage.)
I will say that I think Luke will be largely absent from the film and I don't think he will necessarily be guiding Han to Maz either. I think Maz will end up being someone Han met sometime before, either at Luke's Academy if that was it was or through his smuggling business at some point to help the rebels/resistance. To that point, I think Maz will probably be similar to Lando from the OT. She's a smuggler/pirate (I'm kind of getting the Hondo Ohnaka vibe from TCW regarding the character) that will help our heroes and possibly show up in one other movie in the ST, and that is probably it IMO. Don't get me wrong, I think she knows more about what is going on in the SWU than a lot of other characters, but I don't think she and Luke are in contact.
To your point about Poe being on Jakku because Luke is there, I'm not convinced that is the case. I think Poe is there looking for Luke and is alone to limit any suspicions regarding his activity on Jakku. (Mirrors Leia's story in ANH to a degree when she was seeking out Kenobi.)