Suggest that for each loan application an SAR is made to see what information was provided to take out the loan. And to see how the loan provider dealt with the application. You would want to see that your Son provided accurate information and it is just poor lending decisions being made. The SAR's are now free, so no cost apart from any postage. 

Yes open an new basic bank account with a bank where no debt is owed. Make sure any money including benefits is paid into new account. 

In the CAG library, there are letters which can be sent to creditors. He could cancel any direct debit payments and offer say £1 a month to each. He would advise of his ill health with no current employment income, as the reason for this.