@MrsRaspberry
Oh wow, I think you are having a tough ride on here.
If my family had a friend in need and he had no-where to go, given how long they have known him, I would have probably let him stay too. I think its a really kind thing you did and sadly, sometimes, no good deed goes unpunished.
Sometimes the persona they project to their friends and the reality can be two vastly different things. He was onto a good thing and he still abused your kindness and generosity.
He is not a tenant or a lodger, he is a sofa surfer and you must call him that on any paperwork as sofa surfers do not have tenancy rights, they are considered "Licensees" meaning they can be asked to leave at any time so if you encounter any difficulties you might want to seek legal advice to ensure the process goes smoothly.
Write him a letter, explaining you agreed to let him sofa surf short term whilst he sorted out somewhere to live and unfortunately you have seen little real effort on his behalf to address his situation after more than 8 months. Explain that due to the issues he is creating in your home and the significant costs you are incurring, its not sustainable and as per the discussion on X date, you have every right to ask him to leave immediately but in consideration for his situation, you gave him 2 weeks notice to leave the home with all of his possessions. That means that by x (time) on x date, he needs to have vacated the premises with all his possessions and redirected any post/notified the benefit system that he no longer resides there.
By giving him this in writing you are clarifying that this is not a case of breaking a tenancy agreement so he has no rights but also that you have given him ample opportunity and that he can present this letter for emergency housing.
Make sure you give him it in writing and make sure you change the locks as soon as he leaves.
Your generosity has been taken advantage of but now the impact on your family and financial wellbeing is at its limits so he needs to go.
If he ends up homeless, this will not be your fault. You offered him way more than he deserved and far from being grateful, or being on his best behaviour, it sounds like his behaviour deteriorated and he abused your good nature and your family. Who knows what he did to those he felt HAD to help him, i.e. his Mum and the supported housing residents. Do not let his "friend" in, if they arrive, lock the door and take stuff to the door for him and hand it over.
At some point, individuals need to take responsibility for themselves and he is no longer a child. He needs a wake up call.
Good luck and stay strong.