Get as much of this in writing as possible from Allstate. Then contact your state Attorney General and any state bureau that deals with car repairs and insurance. What Allstate is attempting to do with the repair amounts to fraud. If your local news stations have any kind of consumer troubleshooter segment then contact them too. At this point I would also contact the diminshed value lawyer except instead of settling for 8K I would shoot for the total value since your car will not have any value at all if these inadequate repairs are carried out. One final note - you're in a difficult position if you can't get proper repairs and then sell your car. The way liability is running amok, you may be on the hook for selling a known defective car.

25 years ago I heard how Allstate was a good insurance company - until a claim was submitted.