Your own words destroy your theory. “ It’s Ben Kenobi in the earlier episodes that is truly virtuous, noble and pure of heart. He’s our true hero. He’s incorruptible.” By this very phrase Obi Wan would never violate his understanding of the Jedi Code by making any attachment that would produce a child. He even chastised his master Qui Gon for not following the Code as closely as he should. And I ask how Anakin/Vader didn’t bring balance to the galaxy? Remember how the Old Republic was teeming with Jedi. And after Order 66 and later the Jedi Purge carried out by none other than Darth Vader AKA Anakin Skywalker, how many jedi remained? Last I checked in the OT there were two Sith (Palpatine and Vader) and two Jedi (Yoda and Obi Wan), you cannot get more balanced than that. I don’t know where you got the idea that Luke was to restore peace to the galaxy, His job was to overthrow the Sith leadership of a corrupt government. As for his failure at training Kylo Ren, I’d say he did a decent job, but at what point does the student take responsibility for their learning? Luke left for Cloud City before his training was complete, and then continued his training elsewhere (as indicated by his mastery of suggestion and force choke at the beginning of Return of the Jedi). Perhaps Kylo did something similar, went off half cocked and found the lure of the dark side too much to resist, ore even preferable to the light. It’s like they finished high school and couldn’t decide what college to attend, a teacher who would detain you to continue your training is not educating you, he is indoctrinating you. I imagine Kylo giving Luke the same speech that Luke gave Yoda when leaving for Bespin: “I’ll come back and finish what I begun, you have my word!”
To sum up: 1) Obi Wan is virtuous and would never ever violate the Jedi Code, therefore no progeny. 2) Anakin/Vader fulfilled the prophecy, though not in a way anyone expected. And 3) Kylo Ren failed Luke, not the other way around.