First of all, my condolences for your defect.
From what I've read, we're not dissimilar in terms of our technical background, and I mostly have success with my analytical and demonstrative approach. Except—and this is the big difference—when dealing with Chinese sellers. Comparing them to European retailers with their warranties is pointless.
I've had similar problems with both, wheels and frames, and in my experience, it was like hitting a brick wall. Last time, I was happy that the seller's offer to send a replacement frame, although I had to pay for shipping and customs (150 euros). And this despite the fact that there was undoubtedly a manufacturing defect which the dealer did not dispute.
AliExpress support probably won't read your explanation, let alone understand it. Offering a 10-20% discount is standard practice and usually impossible to increase (no matter how much you argue). Having no guarantee and potentially being left with a total loss is now part of my calculations.
Nevertheless, I certainly hope things are different for you.