Heartless CSA always makes things difficult

My partner is on the 2003 scheme which we hoped would end in August 2016 when his daughter will be 18, as she is staying at college he has to keep paying for at least another year. she can get a part time job and her mother can still take the £700 a month off him. He has never seen his daughter since she was 2, he has taken her to court, she slept around whilst he looked after his daughter and her other 3 kids to other fathers. the system does not take into account any other outgoings and he is at rock bottom having to pay a possible further 2 years. If he at least went onto the new system he would pay at least half of what he does now but how can he get them to do this as they are heartless people and not willing to listen.  I am frightened for him and feel he may do something stupid.  I have 4 children and get nothing from their father as he is self employed and can therefore cheat the system – how is this a fair system??