We've already seen what happens when the results are rejected: Nothing.
As for the military being deployed to voting booths, you do realize that it's logistically impossible to pull that off nationwide, right? (Particularly so in the middle of a hot war.)
It's fine to speculate, but I don't think any of these doomer election fantasies make real world sense. If Donald's going to fuck with the election, it's going to be via the mail system, because he can do that 100% legally.
Americans are going to vote so overwhelmingly against his candidates that it won't be possible to feasibly rig the mid-terms. $6 gas, not being able to afford groceries, and soaring homelessness will mean consequences for the ruling party. It always does.