More nails for your argument's proverbial coffin... ;)

===

> Seriously? You are seriously contesting that a defining characteristic of religion is that it makes non-falsifiable claims?

"Yes, DUH!", hence the question. What indicates to you that making non-falsifiable claims is a defining characteristic of religion?

> The fact that I am measuring the falsifiability of your position does not mean that you are establishing my position.

So you are not relying on me to describe to you a very specific observation that I would "accept as falsification of the claim of the existence of the god that [I] believe in", in order to answer my question "How has it been shown that the claim "God exists" is not a falsifiable claim"?

> Would you prefer if I argued against a randomly selected religious position of other people that you probably don't agree with, and will you accept me demonstrating that that position is not falsifiable as demonstration that your position is not falsifiable?

We already selected the position "God exists". You've yet to demonstrate that it is not falsifiable. You are merely dodging the question with "It just is!"/"Because I said so!" like responses.

> A container with liquid water in it that is measured to be at a pressure of 1 atm and at a temperature of 149.9999 °C, and the temperature of the water vapor coming off of it measuring as 150 °C (or in short: water boiling only at 150 °C). That observation would falsify the claim that water does not boil only at 150 °C.

Measuring the temperature of the water vapor at 150 °C coming off of liquid water at 149.9999 °C doesn't falsify that claim if you haven't checked lower temperatures. If you haven't checked every temperature from -273.15 °C to 150 °C at every possible precision, then you may have missed some other temperature at which it boils. More over, if the claim was "water does not boil only at 150 °C in 1 atm" vs "150 °C+ in 1 atm", then you'd also have to check every temperature at every possible precision above 150 °C to falsify that claim.

> You are confusing "formal truths" and "real truths".

Is it possible to make a tautological claim about reality?

> I have a hard time figuring out what that second sentence means ...

If you can always potentially falsify claim A which is the falsification of claim B, then claim B always has the potential of having not actually been falsified. If a claim always has the potential of having not actually been falsified, then it is not actually falsifiable, because if it were actually falsified then there would no longer be any potential for it to be not actually falsified. For a claim to not actually be falsifiable, when it is said to be falsifiable, is a contradiction.

In other words:

If you can always have the potential to show that claim A is false, which is a claim that states claim B is false, then claim B always has the potential of having not actually been shown to be false. If a claim always has the potential of having not actually been shown to be false, then it cannot actually be shown to be false, because if it were actually shown to be false then there would no longer be any potential for it to have not actually been shown to be false. For a claim to not have the potential to actually be show as false, when it is said to have the potential to be show as false, is a contradiction.

> That's, again, only a problem resulting from your demand for certainty. ...

No, it is a problem resulting from your use of the word "is".

> I mean, you are aware that there are delusional people, right? Like, people who have an almost completely wrong idea about their identity? Are these people justified in being certain that they exist?

In what context could some existing person be certain that they exist and be wrong?

===

Since being falsifiable is your requirement for making warranted claims about reality:

What specific observation can you describe that would falsify the first premise of your argument?

What specific observation can you describe that would falsify the second premise of your argument?

What specific observation can you describe that would falsify the conclusion of your argument?

What specific observation can you describe that would falsify the claim "making non-falsifiable claims is a defining characteristic of religion"?

What specific observation can you describe that would falsify the claim "the claim 'water only boils at 100 °C+ in 1 atm' is falsifiable"?

What specific observation can you describe that would falsify the claim "'formal truths' are not about reality"?

What specific observation can you describe that would falsify the claim "claims about reality must be falsifiable to be warranted"?

What specific observation can you describe that would falsify the claim "there is no way to verify that perception matches up with any sort of 'ultimate reality'"?

===

Have fun!