There isn't much choice. New tires (expensive), alignment, rotation (already performed), driving style (sometimes hard to change).
I agree toe in as part of the alignment should be as close as possible meet the suggested value, not just "within range". I also agree that lower camber (within range) can help reduce wear. I don't agree that camber necessarily needs to be below one degree. Between one and one and a half degree (-1°30') on rear is probably ok on very most passenger cars and small SUVs and will likely not cause issues as long as toe in is spot on. Your Tiguan deserves an alignment and I suggest you post the outcome here. I'd love to see "before" and "after" values". As a hint: Don't let them tell you the Tiguan's rear axle isn't adjustable. Both camber and toe are almost independently adjustable (there's some correlation and both have to be adjusted alternatingly to reach desired values).