2sprightlyboys … You obviously love your boy and clearly want him to achieve goals that will benefit him. I can’t comment on how or why his condition affects his motivation beyond a typical teenager but he is just that, a teen. Low motivational state and grumpiness are very common due to neurological changes and consistent sleep patterns, exercise and diet are important too.
However, his motivation needs to be internal rather than external. Your frustration is obvious but expecting him to meet milestones that he has little no interest in will frustrate him too! Demotivational and negative behaviours are his way of saying you’re on the wrong track. Guilt with only compound your need to become right which is possibly why you want him to fail.
So, this is now not about him validating your needs, but validating your relationship with each other. Call it ‘a need to rebuild trust’.
So, consider this: picture your ideal interaction with him. I’ll guess smiles, kind words, graduate and so on? Make that happen and leave it your agenda! Also find out what he would like to do. It doesn’t matter what it is because you’re not going to focus on the task but his degree of movement towards being involved in his terms. It’s going to take time but you have plenty of that. Concentrate on building trust. Get in with your own interests too as that creates exemplars that he will observe and model his behaviour on.
Our your relationship first and agenda second…
I hope this helps.