I agree with DeeDee - if you can swing private testing I would do it. Private testing is often more diagnostic than school testing and will contain comprehensive recommendations. Schools generally test to determine eligibility and base line for IEP objectives. Their recommendations are often based on "what they can provide" and "resources" rather than what the child really needs. You probably see this with private OT vs the school OT.
Given the issues around understanding verbal instructions and reading comprehension, I would include a full speech and language evaluation along with the neuropsychological evaluation. Make sure the professionals you select are experienced with children, learning disabilities and school. If there are teaching hospitals, universities and or LD schools in your area, they can give you some good referrals.
If you think you may end up in a legal battle with the school district, you should find out if the evaluators are willing to testify as expert witnesses. You can use their report as evidence that he should remain on an IEP and he needs certain services. If you would like the district to pay for the testing, read up on IEE's Independent educational evaluations.
Given the enormous strengths and the significant difficulties - it makes sense to get an unbiased and expert opinion on how to proceed. Based on what you describe, it seems like he should remain on an IEP.
