The only things I would change about your response -
"I take your point that difficult child should have asked for help; but surely you are aware that a major part of the problem is his inability to recognise he needs help, and then further inability to reach out and ask? It is desirable of course for him to be able to ask for help, it is one of the many goals we have. But he is a long way from there yet. It is one more area in which he is greatly disadvantaged compared to his peers."
AND
"I do not believe difficult child deliberately withheld any information from me. I believe he told me the full story, as he understood it to be. His ability to stay focussed on work in class is hampered compared to other students, it is one of the many reasons we have an IEP. Our goal for him is to one day be able to function as an independent, productive and happy member of society. We recognise that his path to that goal will not be smooth and will in fact involve a lot of hard work form many people. It will also take him a lot longer. But nevertheless, it remains our goal."
Other than that - I do endorse your gentler, "easy child" approach. You can catch more flies with honey than vinegar.
Well done!
Marg