As far as the uneven wear side-to-side, I would suspect a sticking piston in the caliper, maintaining too much pad/rotor contact. This may also be a partial explanation for your wonky ABS.
As far as the ridge on the rotor goes, normal.
The rotors will be marked " minimum" xxxx.
If the ridge bothers you, you could have it turned down even.
In regards to your rear brakes, they normally do very little work, as 80% of your braking is handled by the fronts.
Quite normal to see a 2 for 1 ratio ( frontpads twice, to rear pads once ).
