I'll try to respond in the order Conery presents his own thinking.
Luke and The Dark Side
He clearly does not turn. He sees what he's doing, giving in to the hate, and stops. To illustrate, he has the epiphany moment, and turns and tosses his lightsaber away. What I think IS important here is that Luke is the one to bring BALANCE to the Force. Not by helping eliminate the Sith, leaving only Jedi, but rather he found a way to balance the two halves- emotion and logic. It's even shown in his having one dark glove and one bare hand. He pleads to his father for help, and Vader once more becomes Anakin- love overcomes hate.
Seriously, if Luke had turned, he wouldn't know the Emperor had the lightning ability, nor would the Emperor have said, "So be it... Jedi." This was the moment Luke became a true Jedi Master. By rejecting the Dark Side."Good. Now fulfill your destiny, and take your father's place at my side.""Never. I'll never turn to the dark side. You've failed your highness, I am a Jedi, like my father before me."
This ties directly into Conery's next portion- he believes that in Yoda's infallible wisdom lies unalterable truth, "Remember your failure at the cave." The vision showed Luke's path to becoming his father. Or conversely, that his relationship to Vader was being revealed, which could jeopardize his chances to save his friends. So, yes he was being impulsive and hasty, but he was also relying on the Force to guide him.
"Only a fully trained Jedi Knight, with the Force as his ally, will conquer Vader and his emperor. If you end your training now, if you choose the quick and easy path as Vader did, you will become an agent of evil."-YodaJust because Yoda is seen as the wisest being doesn't mean he is truly all-knowing. Right before Luke leaves Dagobah for Bespin, Obi-Wan says about Han and Leia, "Even Yoda cannot see their fate." Yoda doesn't necessarily know the future. This is shown once again in Attack of the Clones, when Obi-Wan and Yoda are wondering why Kamino isn't in any of the Jedi archives, a youngling student suggests maybe someone erased it. A small untrained Jedi child saw something quite evident that the 900 year old Master missed.
Later, when Luke returns to Dagobah Yoda has tells him, "No more training do you require, already know you, that which you need." With the message that he only has one more thing to do to become a Jedi- to confront Vader, which as I said above, he did. He became a master by rejecting the Dark Side.
"A Jedi shall not know anger. Nor hate. Nor love."
What Yoda didn't account for is a new form of Force user, one that CAN use emotion as well as the Jedi logic. The Jedi failed because they cut themselves off from attachment. During the final battle, Luke gives up his weapon- as Yoda also said, "A Jedi uses the Force for knowledge and defense, never for attack." Clearly, through the Prequels we see this isn't exactly something they follow themselves. Over time, the Jedi became detached and the Sith became overly attached. The wedge drove the two paths to diverge further from each other than they may otherwise would have.
Anakin was touted as being The Chosen One, to bring balance to the Force. Perhaps he did, but not how many people think. In the end, Luke appealed to Vader's love for him to overcome the Dark Side, resulting in his redemption and the death of the Emperor. I think Anakin brought balance by having Luke, and both of them learn that emotions aren't the evil the Jedi taught. It was their shared connection that allowed them both to go on. It was the way Luke found the path between using logic and emotion together.
Luke Lying to Jabba
For one, he's not lying to the Emperor. He did lie to Jabba, but you know what, Obi-Wan lied to some stormtroopers. He even used the Force to do it. Sometimes the Jedi lie.
"Who is Luke Skywalker?"
This is a key element here. Kathleen Kennedy got J.J. Abrams to come on board the film by asking him this question. It is really important because he is currently the pivoting point for the Force itself. He is the last of the remaining Jedi. As Han Solo points out in the full Force Awakens trailer, "It's true. All of it. The Dark Side. The Jedi. They're real."
These things have fallen into myth. They are rare and nearly forgotten, and only one person has answers left- Luke Skywalker. He is the last true light against the rising darkness of the remnants of the Empire in the First Order, and he's in hiding.
"The Saga films focus on the Skywalker family saga. The stories follow a linear narrative that connects to the previous six films. The Force Awakens follows Return of the Jedi and continues that generational story." -Lucasfilm President Kathleen Kennedy
The Force Awakens may be a continuation of the Skywalker legacy, but as the original trilogy and prequels passed the torch, I believe this is another case of that- Luke's importance doesn't necessarily mean he's the film's focus. And as I've previously mentioned, he's probably hiding somewhere. Luke has become the Obi-Wan Kenobi, the mentor to a new generation of Skywalker.
In the first Star Wars related book for the new series, Aftermath, there's an interesting tidbit. It's got a familiar red bladed lightsaber being sold to three ominous looking figures, and there is also a picture on the wall of a Vader helmed head with the words, "Vader lives" written by it. I don't think Vader is alive, but that with all the time that has passed, the miraculous way tales get spun, maybe Kylo Ren is trying to use that feared name to become the Dark Lord of the Sith in his strange obsession. Maybe he's trying to clone or resurrect him or something, I don't really know.
And lastly, the most obvious reason I think Luke is still good. This Kylo Ren toy mask says, "Together we will destroy the resistance... and the last Jedi."
If Luke did turn to the Dark Side, it would've long after Return of the Jedi. It's more likely he's simply in hiding, and hanging out with his Force ghost buddies. He might even be a Force ghost himself, but I highly doubt he's evil.