Loans from a family member

Hope someone can help on this one!
My son has recently split from his girlfriend. They jointly owned a house and he pays half the mortgage plus his share on a secured loan, this amounts to £348 monthly. He owed £10000 before buying the house and in order to get his mortgage we arranged a loan through our mortgage supplier in our name to pay this off, as we pay interest only on a very small mortgage. He pays £70 a month into our bank account by standing order. On top of this he has credit and loan payments, and numerous bank charges because there is never enough money in his account in time to pay all his direct debits. The bank charges we are trying to get back thanks to advice on this site and the Consumer Action Group site. but his debts apart from his mortgage are in the region of £30000. Because his half of the secured loan is £10000 and he owes us £10000 he doesn't seem to be able to get any help from anywhere and never has any money. Obviously his credit rating is not good. If it was possible to wipe off our loan, we would, but I am retired on a state pension and my wife is disabled.
Please, any advice?