2/ So, when Luke takes in his Nephew, he finds his nephew is not only turning to the dark side, but he's powerless to stop it. He goes to confront his nephew, and looked into his nephew's heart. And in one instant moment, he saw the darkness in him and how much Snoke had already turned him. In that same instant, he thought he could stop it. So, like his father, Luke ignites his saber with that fleeting moment of intent to kill his student as Vader/Anakin killed the younglings. Luke saw what he was doing was wrong and immediately felt shame.
Kylo saw this as an affirmation of what he believed about Luke and instead followed in his grandfather's footsteps. The Order - destroyed. Just Like Yoda, he confronted the dark, failed, lost his order, and went into exile.
====== So what does this mean for Luke?
Luke is experiencing PTSD. Luke recognized that if Kylo Ren would become the next vader, there would be untold amounts of suffering once again. 'Lo and behold, Kylo ren did just that. So, Luke saw that the Jedi Order in their teachings were flawed as the same thing kept repeating itself - especially with his blood line. And worst of all, Luke let his legend of being Jedi Master cloud his judgement. Pride so goes before the fall.
===========How is this relevant to anyone?
If you've been abused by people in your family, you may see parallels with generational trauma. Generational Trauma sees the same abuse suffered again and again, with the next generation doomed to repeat it. Rey walked Luke's same path, but it was Yoda who gave advice to Luke saying "Pass on what you have learned. Strength Mastery, but weakness, folley, failure. Yes, failure most of all. The greatest teacher failure is. Luke, we are what they grow beyond, that is the true burden of all masters."
If not for being a parent, you can take this lesson and see that it's normal to fail. We live in a society where perfection is expected of us, and we shy from failure. This movie speaks out against that.
I *really* think Luke lead a life of which his Father Anakin, and Mother Padme would be proud.
Give this video a shot, you might see it.
https://www.youtube.com/watch?v=1kjEnDj7K30