The main claim is that one can run computer simulations on the cosmological constants and see that many other forms of life could be possible in other configurations, which contradicts the fine-tuning argument that says specific constants were necessary for life to be possible.
Second, at the end of the video he points out that seemingly it makes no sense to create such a huge universe for life on one particular planet.

I addressed this in the book. These are fairly exceptional cases. The simulations that were done made very strong assumptions, and the “life” produced there is temporary.
As for the logic of creating such a vast world, that’s a silly argument. 1. He decided that the purpose of the universe is human beings. Who said so? 2. If God’s way of thinking doesn’t make sense to him, then apparently he doesn’t understand it. The question of whether the world was created or not has nothing to do with whether it makes sense to create such a world, but with how probable it is that such a world would arise on its own. In the book I explained it this way: suppose you find a very complex watch on the seashore, built in a way that seems very strange to you. Does that mean it came into being on its own, without a watchmaker? What determines that is only the complexity of the watch. The fact that it was made in a way that seems strange to you only means that the watchmaker’s way of thinking is different from yours.

Fine-tuning includes a hidden assumption about God’s nature and actions—what God does and what God does not do. And that always strikes me as suspicious.

The refutation of fine-tuning is actually pretty simple.

Imagine that God created all the universes that can be created, with all possible laws and all possible constants. Naturally, we live in a universe that allows this.

From such a state of affairs, you cannot prove what the argument claims to prove.

Rabbi, what do you think about The Last Decisor’s response?

I also addressed that in the book. Briefly:
A. It just pushes the question back to who or what is the generator of universes that produces all these universes.
B. Where are all those countless universes? Every single one of them is invisible?
C. Why is the theory of countless universes simpler than God? One should remember that there is no possibility or need to reach certainty. The question is what the most reasonable conclusion is.

And what about the argument that it makes no sense to create such a huge universe for such a tiny creature that can’t use almost any of the universe?

It would be appropriate to read what I wrote before asking.

In this view there is no generation of universes. Everything that can exist does exist.
Where are they? They are immersed in their own existence, without interacting with other universes.
The theory is not one of countless universes, but that everything that can exist does exist.
What can exist? We do not know. There is no way to know.

The theory that everything exists is more plausible than a theory that says that out of everything that could exist, only a universe identical to ours exists—which is childish thinking to begin with.

If everything that can exist does exist, then God exists too. Boom—destroyed with facts and logic.

It cannot be known what can exist and what cannot.
Besides, God by definition is something that necessarily exists, as opposed to something that merely can exist.

In any case, I only came to refute the fine-tuning argument. I did not come to prove what exists and what does not.