$40-$95K per year was unfortunately still too high to be approved and it makes sense you were refused. The annual costs need to be $20K or lower in order to be approved. This is what you needed to prove in your response to the procedural fairness letter in order to override the medical admissibility.
To the best of my knowledge, to win under judicial review, you have to prove that IRCC was wrong in the decision they made. I'm not sure how your lawyer plans to do this and you would be best off working with him/her to determine this. I think it will be difficult given your response to the PFL letter confirmed that your son's annual health care expenses would exceed the $20K maximum per year.
You may want to spend time researching appeal cases through the canlii web site to see if you can find cases similar to yours and what the results of the judicial review were.
https://www.canlii.org/en/
Good luck.