Rear tire wear & camber question?

[VR6TUNER]

Ok so I bought the car about 5k ago and notice that the left rear camber was noticeably more than that of the right rear. If you stood in back and looked at it, it looks like it had twice the negative camber. The tire wear on the left rear was real bad on the inside almost worn all tread slick. So I checked tire pressure and it was at 30lbs in both but the door said 39 so I put them where they needed to be and took it to have it alligned. I told them my main concern was to check the negative rear camber on the left side. Well they checked it and told me I actually had some toe out on the right rear. So I say hmm. cause I took the left rear off to check the brakes and the wheel had RR in it from when tires were put on it. So I figure that they notice the wear on the right rear and moved it to the left just rotating instead of fixing cause they were selling it. So I ask them about the camber and they told me it was within specs, and gave me a print out, but its still alot more than the right side. Well now 4k miles later the left rear has some threads showing through on the inside of the tire, I've been monitoring pressure and its good always. My question is does anyone have any idea why my one side has so much more negative camber and what are the exact specs as far as the amount of negative camber it can have in the back. I have the print out and just off the top of my head they said it was like -5 to -6 degrees, I have a new tire on the way but don't want to install it till the problem is solved. I wouldn't worry about it if it way your normal wearing but this tire has rapidly progressed in 5k miles I'm very confused