Missing optional resume in graduate application
It seems as if you have done all you could. If they won't accept supplementary material, then they won't. I'm not sure about the comment on not reading letters, though. It seems like it would be a flaw in the system as long as the letters are in (readable) English. 

If you get past initial screening you can raise such thing in interviews or in future correspondence, of course. 

And, take more care in the future, of course, though it doesn't help at this moment.