Lemme get this straight. If Davis had just stood fast, Lincoln would NOT have invaded the South?
Is that what you are saying?
Lincoln lacked the political or popular support to force the issue through military means. So no, had Davis not fired on Sumter then Lincoln could not have sent troops to force a reunion. Or if he had then the south would have been able to claim that they were the injured party. Status quo worked for Davis far more than it did for Lincoln. Had the south held fire then it's likely that the confederate sovereignty would have been recognized by default by the summer.
Is that what you are saying?
Yes.