I was wondering why did Ren kill Tekka instead of interrogating him like later with Poe? As much as he knew, Tekka might’ve been the only person to know of the map. What if he didn’t find Poe after killing Tekka?
Also, how did he know that Tekka gave the map to Poe? Did he read Tekka’s mind? Tekka might be old, but doesn’t seem to be weak-minded (except when he goes straight to them to get captured 😄 ). So, did he read Poe’s mind, instead? That would be odd too, because he later has to interrogate him for quite some time before he can get the informations he wants.
For the first part of your post… I took it as both Tekka and Ren knew that Ren wouldn’t be able to interrogate that information from him - whether that is due to Ren not having finished his training / skills - or Tekka having some knowledge (of the force) to be able to resist him. So if Tekka would not give Ren the info then Ren would ensure no-one else would be able to get it from Tekka…
It wasn’t made clear enough though - if this was indeed the case.
Re the second part - Ren knows and acknowledges that they have captured the best pilot in the resistance in Poe - so he likely knew that was the reason Poe was on Jakku - to meet with Tekka - likely re the map / or Skywalker’s whereabouts…
Just my guess at it.