Well, I personally think that you just very clearly articulated the problem and should print off your response to me and present it to the teachers/sped team! That was a very clear and succinct example of how his disability limits him in regards to his strengths. Have you explained it that way to the teachers?
Here are suggestions I would have for the team if I were the OT on it:
1) first you need to look at two approaches: remediation and compensation. Which are you doing? You need to decide as a team whether you are going to provide services that remediate the deficit areas or compensate for them. Or a combination of both. Since the parent and student are a vital part of the IEP team (see IDEA federal law) then your and Mite's preferences should be taken into consideration. Since he wants to write, then remediation should be part of the IEP, until such time that it can be proven that he won't make improvements or the Mite decides the process of writing just isn't worth it.
2)Remediation: I would look into Interactive Metronome. Have you tried Handwriting Without Tears? What about a pure SI based intervention - has he ever been assessed with the SIPT for sensory integration disorder? You might need to go privately for that one - most school based OTs don't use the SIPT (Sensory Integration and Praxis Tests) and don't/can't provide a pure SI based approach.
What spelling techniques or programs has the school tried? Slingerland and Orten-Gillingham are two names I know of, but not being a teacher I can't really say what the difference is or whether they would help Mite. But what do the examiners who have seen him say? Any recommendations there for specific interventions for improving spelling?
3)Compensation: you need to have Mite's buy-in. He needs to agree to use compensatory techniques AT TIMES in order to produce the work or end-product he desires. In the case of the letter, it would have been great for him to have a computer program such as Dragon Dictate. He could just dictate the letter and the program provides the spelling. It would give him the independence of not having a scribe write what he says. A low tech version of this would be for him to audio record his letter/writing and someone write it out later. At least that way Mite won't feel hampered by how fast/slow the scribe writes his words and he can just let his thoughts flow. And he won't feel like he is so unique - tell him doctors dictate all the time!
From what you say the hardest part must be that Mite is so acutely aware of his difficulties and so stifled by them, in terms of his abilities. But, the flip side of that is that with the right support and encouragement Mite is bright enough to understand how he can accomplish his goals, even if he never learns to write cursive. Eventually that goal won't be so important to him. He will move on and decide that he wants to PRODUCE not struggle with the process. My experience is that even children need to be allowed to work through that self-recognition process. It's a matter of coming to terms with one's own limitations and embracing one's own strengths. People with disabilities have to do this every day. And we all have disabilities to one degree or another. We are all hampered by relative weaknesses and demonstrate relative strengths. And we each need to learn how to make the most of our strengths. And deal with our weaknesses. Mite is just beginning down that road.
For kids, I always talk about how everyone is good at something, but no one is outstanding at everything. I'm sure that Mite could identify kids who can't do things that come easy to him. Maybe that would help him to see his own strengths. Another thought is to see if you have a Center for Independent Living around you somewhere. They are community based advocacy centers run by people with disabilities to serve people with disabilities. Most have a youth advocate on staff, but they all have people with disabilities who do peer counseling and community advocacy. The services are free. Perhaps that would be a place for Mite to meet other kids with LD or other disabilities, and some adults who have succeeded by accomodating for their LD or similar disability. Maybe then he would be able to focus on his own strengths.
Sorry, I got on a soapbox! Stepping down now! Hope this has helped.
