Is it possible that he is depressed? A mood disorder can affect one's desire to do things.
If not, what makes one happy is not the same for everyone. Contentment is hard to obtain. He may be confusing contentment with complacency. In that case, you would be assisting him in realizing the difference. Living at home is in a way enabling him to not try and get out of that situation. You have done more than enough based on what you've listed under "already tried." Try to find out what is it that makes him feel alive. Is it helping others, not interacting with anyone, not experiencing stress (avoidance), etc. If you believe that he is staying at home because it offers predictability, safety and security, if you are helping him get any of that, you'd want to halt your assistance in those areas.
There are different opportunities to take him out of the home even if it is volunteering for the red cross, etc. You may suggest to him to think about working with a counselor or a personal coach. Changes will occur only if he truly wants a different life. Behavior is driven by purpose. His purpose may in fact be to do the least possible.
Get What You Want!: Workbook to Reactivate Your Passion for Life, Find Your Purpose and Achieve Your Dreams Kenneth West
The contentment may be something he is experiencing (it would depend on different factors such as his mood, anxiety level, comfort in social situations, etc) It may not be just for you benefit (the behavior can be learned and he can be used to it. Sometimes helping is causing one to feel enabled and reliant on others to save them from whatever it is - work, stress, keeping up with the Jon's life style and so on) You can help him to an extent (the fact that his behavior remains the same is not an indicator that you have failed. It only indicates that this is what he had chosen for himself) You can help him to an extent by asking him to define what his passion is (even if he works with a career coach. Some things ought to be addressed professionally and he may open up more to someone else ) Passion can be anything- art, helping/altruistic behaviors, etc. You can talk about what interests him (there should be at least 1 thing he ought to identify as interest) Also, ask him if he feels depressed (sometimes individuals may say that they feel numb and not necessarily know that they are depressed) Think about asking him to find his own place or to pay room/board fees should he decide to leave at home. If you're giving him any spending money, halt that right away. Sometimes people do things out of necessity (finding a job) Change your behavior and see if that leads to even the smallest change in him. If you do the same over and over you'd get the same results. Take an inventory of how he spends his days now and that will have to change.