Have you contacted Continental? Continental, actually has a reputation for being a bit above the average production trailer.
I doubt that a frame out of plum would affect tire wear. The axel asures that the hubs stay true. That is, if the wheels are properly tightened, and the bearings good, the frame transmits load to the axels and the axels keep the wheels in line.
Are you certain they’re stress cracks? It’s normal for the surface of aluminum to look a bit frosted where it’s bent. If they’re true stress cracks that relates more to the ability of the trailer to carry load than wheel alignment.
If you post some picture, we may be able to advise you better, but your first line of defense should be contacting Continental or the dealer that sold the trailer.