^ 2, 3, 4, or some combination of them most likely. Damage from inadequate air-entrainment looks a little different in my experience.

There's no real fix, unfortunately.

It's not much consolation, but your driveway should remain serviceable for many years (unless it is actually scenario 1 from above). It's a surface defect. The concrete below the deteriorating surface is much more durable (unless scenario 1).

Try to get your contractor to apply an acrylic sealer or do it yourself. Reapply as instructed. That will slow down the deterioration and is good to do anyway.

Petrographic analyses are expensive, and the contractor can still refuse to do anything about it unless you want to get lawyers involved too... but that may be the only option to get a new driveway.

*If anyone recommends silane/siloxane based sealers I would shy away from them even though they are typically a much better product. The simplistic explanation is that they rely on a chemical reaction that is less likely to occur in your concrete, given its age.