Get the rear replaced and don't EVER use the rear defroster again (price to pay for tint), also don't EVER clean your windows (inside) with anything than plain water.
I've had tint on my last couple of cars, I followed what the installer told me and have never had a problem with fading or bubbling.
I clean mine with non-amonia cleaner, (most all car window cleaners) and they are still good 5 years later. Also I don't see why the rear defroster would be ruined if the tint is removed properly.