I am wondering if you need to check the rear transaxle mounts. 1" out of alignment should have caused some serious buckling of the frame somewhere that should be obvious.
You also need to check the angle the steering arm is welded on each front spindle. They should be mirror images of each other.
That said, You may still have to bend the front axle drag links to get the steering back in fairly good alignment. Deere may have adjustable drag links available like Husqvarna does for theirs, but they may cost so much it is not practical to install them.