True.
But Pascal never said it was the ONLY reason to be a Theist, or even that it was the BEST reason to be a Theist. All we need to see is that it is a very, very, very good reason not to be an Atheist. And that's quite fair. We need put no more weight than that on the argument here. It's enough.
And, on your side again, any Theist who thinks belief matters is going to agree with you about sincerity being key. And any Christian is going to agree with you that you can't "appear" to believe things you don't -- at least not to the eyes of God. No problem there.
But any Atheist has to know he's playing Russian Roulette with his own soul, and with six bullets in the gun. There is literally no way for the Atheist to end up in any good place -- and that by Atheism's own account. They can die and go to dust, or they can face Judgment. Neither alternative has the taste of a win in it. Both are huge losses.
So why is that not very obvious to them? Can't they reason?