Well, at least you got back to the first error and eliminated the bootloader as the cause of the verification error. Unfortunately I just don't know where the specific problem is that's causing this. Certainly the CH340 is one link in the chain. You could test this by using a separate USB-TTL serial adapter to do the upload (that's the purpose of the CH340). It's possible to use the Uno for this purpose, though it's a bit easier if you own a dedicated USB-TTL serial adapter board or cable.