Well, you gave me a lot to respond to. I'll try.

DEFINITELY the kingdom and the second coming are two different things. Definitely. The kingdom of God exists on earth at present, in a less-than-perfect presence, in the form of the church, under the new covenant, as you have said and rightly understood. When Jesus comes back (the dramatic return), he will establish his kingdom in its fullness on the earth.

The End Times is a deep and complicated study. it's one of the reasons Jesus said to study it, but we'll never figure it all out. We were given signs, not the whole map. Many different words and concepts are used, and many scholars try to piece the puzzle together with very deep study. They do good work, though the facts can still be elusive.

In Luke 3.9, the reference is a rebuke to Jews who think they get an automatic ticket to heaven because of their heritage. John is telling him that the only free ticket is through the Messiah, Jesus, and unless they repent of their sins and turn to Jesus, they will be judged just like anyone else.

You're right that Jesus often speaks in metaphors, parables, and riddles. Even his miracles are often "parables in life," with what is actually going on in real time and space being a metaphor or parable of a spiritual truth. We always have to be looking and reading below the surface and in the context when it comes to Jesus.

In Luke 12.54-56, Jesus is saying that we all become at least minimally proficient at observing certain signs about the weather and being able to tell to some extent when it's going to rain or clear up, or whatever. The problem Jesus was addressing is that despite even rudimentary capabilities for such things, they were not able to tell that God was standing right in front of them teaching them the mysteries of the ages. Jesus sees an obvious disconnect where there should obviously not be one. With the training they've had, the opportunities to connect with God, and the insight they claim, if their relationship with God had just a mustard seed of reality, they would be able to do this. Their spiritual blindness is telling, and he calls them on it. Why? Because they’re the leaders.

As far as Luke 21.25-6, oh, there will definitely be signs. But it just tells us "there will be signs in the sun, moon, and stars." They may be "natural" occurrences, though (like, oh who knows, a meteor hitting the earth, or a earthquake/volcano event), and people will say they're just natural disasters. But people who are looking for the signs may be scanning the heavens for Jesus. They can't be sure, but they'll be alert. That's what I meant. It's a sign, but not a certain marker.

You've asked a lot in one question. Ask more. I'm glad to talk to you all you want.

Hmm, all right. Is it sort of like the Kingdom and the Second Coming are two different things, then? That there is an earthly Kingdom, represented in the new covenant, but that it will be followed by a dramatic return?

Part of my issue is that there's a lot of different terms he uses for things that my commentaries (I'm reading the ESV study bible right now) just identify as references to the end times/second coming without going into why they are definitely end times references and not metaphors. I didn't keep very good track as I was reading, unfortunately, but stuff like Luke 3:9 ("Even now the axe is laid to the root of the trees") just gets a little "oh, yep, that's the end times" note and then they move on. Is it based on comparison with other Gospels? Jesus spoke in metaphors so often - why are some parables such as the Great Banquet (Luke 12:24) or the Ten Minas (Luke 19:11-27) taken to be about a literal return, instead of about judgement after death or other more prosaic consequences of being sinful or failing to keep God's words? (There are other parables like the rich man and Lazarus, and the rich fool (12:13-21), that do seem to be simply about consequences after death rather than a final judgement.)

And as for the more direct issue of signs vs. no signs, just from flipping through I have 12:54-56 where he berates the crowd for being unable to interpret the "present time" (which seems like the same context in which he tells the Pharisees there are no observable signs that the kingdom i.e. Jesus is among them, beyond the evidence of faith), as well as 21:25-6 where people are "fainting with fear and with foreboding of what is coming on the world", and "signs in sun and moon and stars, and on the earth..." which doesn't seem to fit with what you said about the coming being simply a surprise. It does still feel like a bit of a contradiction to me, I'd be grateful to hear your interpretations!

In Luke 17.20, Jesus is saying that the close watching of external phenomena will not reveal to people, all by themselves, the coming kingdom of God. People think that by studying the Scriptures they'll have it all figured out, but Jesus himself said you'll never figure it all out. It's gonna catch us by surprise. Now, some will be expectant and ready, and will have enough of it figured out to recognize it when it comes, but it doesn't come with your careful observation.

But when he does come (Lk. 17.24), it will be plain, unmistakeable, universally visible and recognized, seen in every quarter of the world.

Is the kingdom of God "coming in ways that can't be observed" (Lk. 17.20), or will it be "as lightning flashes from one part of the sky to another" (Lk. 17.24)?

Background: I'm a former atheist finally beginning to explore my faith, and I've started a bible reading plan that so far has taken me through most of Luke. I see most of Jesus' teachings as being primarily concerned with a kingdom that is here, the creation of a "heaven on earth" through good deeds and righteous living, so I'm confused by the times when he suddenly seems to speak of a literal end times. Why does he speak of a Kingdom that will not be recognized by unbelievers in some passages, and a literal, easily recognizable judgement in others? How do Christians resolve these passages?

I do have my own pre-existing ideas about the nature of God, Jesus' teachings, and the resurrection but I'm genuinely interested in hearing what long-time believers think.