What company are you with? Are you in rented or your own accomodation.
I would challenge that, I am sure most IP's consider the needs of disabled children, or they should do, mine did.
What if your son was to go into accomodation or a special residential college? Not saying he will or should but...... My son goes to school 25 miles away, he has transport but if he is ill at school (he suffers from a heart condition, epilepsy, etc) so it can and does happen, how would I be able to afford to fetch him without the extra money for petrol?
My kids were given suitable allowances to enable them to have some quality of life.... so should yours. I wash more, dry more, buy special food, take them out etc, etc, etc..
~The way I see it, if youre in a position to go BR you will have more weight then if youre not. If you are trying to keep your own home, the IP might not budge. I would still challenge it, the only problem I can see is the fact that you signed the money away, with that said its a stressful time and many agree to anything for peace from calling creditors.
Good luck and please come back and let us know.