My oldest son, ( a twin) is 40, he too still lives at home, he too can be economical with the truth, he too can not keep a job, we never get to the bottom of why this is. We have struggled with these issues since he was in his early 20's. About 5 years ago we sought medical advise ( again) asking for him to be tested for Autisum. I had read a book by Tony Atwood an Austrailian who works with & has written extensively about people with Asperger's Syndrome. Reading this book was like reading about my son!
The result was positive. You may say that gives our son a label, yes it does, but it also helps us to understand a little bit about what we are dealing with. The issues are not solved, they don't go away, they are there daily. Fortunately my husband & I are able to supposrt each other with all this brings, but we do worry for the future of our son as there really is not much out there in the way of support for what is termed as high functioning Adlut Autisum. We are in our early 70’s & it must be said it has affected our retirement both emotionally and financially. Maybe you would be wise to seek further advise. Good luck.