Maybe you could explain (no pun intended) why it's not an explanation? Go back to the card example I used earlier - would you agree that me intentionally arranging the events is an explanation? What exactly is it that makes this an explanation, but not an intelligence behind universal constants (I won't use the word God so as to not offend you---again, the idea that there is an intelligence behind universal constants doesn't commit us to any particular faith, doesn't commit us to the idea that the intelligence must be the ultimate cause or omnipotent or omniscient or anything like that)?

>All it does is move the goalpost for explaining beyond unreachable and trap the inquisitive mind in a box.

What box-trapping are you referring to here? If by moving the goalpost, you mean that it doesn't explain anything about why the intelligence is what it is or how it behaves---yes, indeed, it doesn't, and we're still open to asking these questions. Again, we're not committing to any particular faith here, you could even use this argument to provide credence for the simulation hypothesis (something you're probably fine with since it's not a strictly theistic idea), since we're not saying anything particular about what this intelligence is like or how it came to be. In the context of the argument, we say "God" to just mean "intelligence behind the universe".

>As to the predictive power, the multiverse theory does have it. The fact that we can't experimentally confirm it today doesn't mean that it's not falsifiable.

Oh, interesting, what are you referring to here? What could empirically falsify the multiverse theory?

>Again, just like with intelligent design, there is not a single physicist who was an atheist first, and then learned about fine tuning and became a believer. Every single proponent of fine tuning was a person of faith first (predominantly Christian but some other faiths too) before they became a physicist. Can you name a single counter example? (that might make me reconsider)

I don't see why the behavior of people who accept or reject the argument is relevant. We don't reject intelligent design because it's pushed by Christians; we reject it because it appears to be inferior in terms of explanatory power and utility for scientists. (Of course, intelligent design is still an explanation; another key point here is that there's a difference between a false or bad explanation and a not-even-explanation---off the top of my head, I can't even think of what a not-even-explanation that purports to be an explanation looks like.)