MLZ ~ That’s tough if it’s functional challenges because there may not be any motives beyond a lack of understanding. I’ve dealt with something similar but not really parallel to yours when I moved back to the mainland to recover from a health crisis.
I worked from home caring for a female in her late 20s who lived with me. She was DD but high functioning in some ways. She drove her own car and was a spoiled daddy’s girl. His GF gave him an ultimatum (It’s either me or her) so they were looking for her first placement outside of their home. The issues were many with the main one being she was morbidly obese and stayed in bed most of the time. She was fairly non-verbal at first but over time that improved. After a couple of weeks of hitting the fridge every hour and lounging I knew I had to implement something, without much help from the team of ‘experts’ assigned to her case. For me it was hard to determine how much of it was a lack of motivation until I could observe her behavior for a while.
Once she felt comfortable I tried using a life coaching tool with her called ‘The Wheel of Life.’ It’s basically a pie chart with 8 segments. On the outside perimeter of each segment you write in important parts of your life. Ex. Work, school, exercise, social life etc. in terms of what’s most important and prominent parts of your life. (In her case ‘buying more CDs was one of them.) On the inside of each segment you write in aspects you hope to achieve, improve on or want in relation to the subject. Ex. Under ‘Health’ - Lose weight, improve diet etc. The goal is to give each segment equal attention on a regular basis to create more balance in your life. As you revisit the chart and work on attending to the lists, you see what goals have been achieved and one’s that have been ignored. Then the shift goes towards working on those. For people who are learning disabled, there could be only a few aspects or segments in their lives and each are overloaded.
I started with her filling out the chart over dinner. It was probably the first time anyone had a conversation with her about what her goals and interests were. (Mom and dad were functioning alcoholics who wrote her off from a young age). One of the goals was to find a job. Within a couple of weeks she accomplished that. We would take the chart off the fridge periodically and cross off some things she had accomplished and added some. She wanted to save and keep using the original chart. I think for her a visual tool was helpful.
She didn’t miss a day of work for months. When I would say ‘I’m proud.’ I know she derived a lot of satisfaction and self esteem in hearing the praise.
Although your son is older and higher functioning, there are times when everybody hits a wall in life. Maybe finding something that would interest him and motivate him would help. Ex. Taking over the property upon your passing, finding another type of work in addition to MS etc. (one that he could manage without additional guidance)
I would try a different approach other than you doing the coaching, as he may view you as his equal. Maybe someone who can act as a coach and you each do your own wheel, guided by them. There are a lot of non-profit vocational programs out there that may be on board with providing assistance in getting the wheels churning. (No pun intended.)