My tolerance ends the moment someone else is intolerant of me.

That’s legitimate. I’d say it’s even the only case where intolerance is legitimate.

Christians think I am going to hell and plenty of them would happily kill me if they thought they could get away with it. I won’t tolerate that.

Some think that, some would do that. And you’re 100% right not tolerating that. But none of that is inherent to Christianity.