You are overlooking the fact we would replace unstable opec oil with our own. We would need to produce enough to cover domestic use and have enough surplus to export. All of your dollar fears could be triggered over night by a stiff political wind in Saudi anyway.
And your overlooking the fact that dollar hegemony is just as vital to our national interests as massive amounts of oil. I would argue that it is more vital in fact. All of western capitalism is hinged on our reserve currency status and that fact is not lost on the enemies of western capitalism. This is why we do the, apparently, crazy things that we do. Our entire foreign policy is built up around maintaining this arrangement. If it ends, the house of cards collapses. There’s no way we’ll let that happen.