We have no idea what Tekka (I assume that’s the von Sydow character?) was doing on Jakku, he seems to have a history with both Leia and Luke and if Rey is Luke’s daughter, it wouldn’t seem implausible that he is watching over her. The Falcon ending up in the same spot is indeed a stretch.
Regarding the damn lightsaber, it should be obvious that a tiny lightsaber behaves very differently than a huge human body, so it may have passed the whole tunnel to whereever it leads, instead of being dropped like Luke. It’s then not hard to assume that Maz has a special interest to gather Jedi artifacts, given her age and knowledge about Jedi and the Force. She runs a bar that has dozens, if not hundreds, of visitors daily, so over a course of 30 years, she may have stumbled over a lost lightsaber, aquired it and stored it until the time would be right. When Rey came to her, the time obviously was right, so the saber “called out”, or whatever you want to call it, for Rey. That’s basically the Force at work, creating small coincidneces over a long time to get things ready.