This is a bit of a tricky one, and I know the answer is probably not going to be the one I want to hear, but I'll put it out there anyway.

DH is his 16-year-old BIL's legal guardian (their mum died and dad is in prison), and since their mum died in August last year BIL has been living with us and claiming Youth Allowance, classed as 'independent'.

The arrangement was made on the basis that he could be treated as an adult and be responsible for his own money (he has worked part-time since he was 13 so we thought he could be trusted to act responsibly as he's had control over his own small paycheck for the last few years), and paid us $50 a week 'rent' which is designed to cover things like food, power, and general living expenses (phone bill is extra and he knows this, and sometimes pays his share when I work it out when the bill arrives).

But, since August, we have been lucky to get $50 once a month, if that. He eats all the food, uses a lot of power, SOMETIMES pays his share of the phone bill (but then seems to act like 'Oh I just paid you $80, I don't have to pay 'rent' for a month now'), and DH and I are going mad broke without his input.
We don't think we're being unreasonable - he gets just under $400 a fortnight, and we're asking for a small fraction of that to cover HIS expenses, not to go out and buy ourselves new clothes or video games, kwim? We are not asking for money to make a profit from him, but to keep our own heads above water.
DH has paid all of BIL's school fees, uniforms etc since the start of this year, not that BIL has bothered showing up to school - he was accepted into ATC (a pre-apprenticeship program) and DH paid the $700+ fees out of our savings, BIL hasn't paid us back OR done a full week of school since January.

So my question regarding Centrelink is, is there a way that we can change the bank account that BIL's YA gets paid into? I know a lot of parents who have kids receiving YA or similar payments get them paid to the parent rather than the child, so the parent can actually spend the money on school stuff or necessities like food, bills etc - I know it's probably a bit late now, but can we go and get BIL's money paid to DH instead, as his guardian, so that DH can use the money to pay whatever BIL owes and then give him the rest of his money to spend as he sees fit?

It's just getting so frustrating. The new baby is due any old minute now and BIL does stupid things like leaving the fridge door open overnight, laying to waste nearly $100 worth of groceries - which I will now have to pay for out of my own pocket, despite the fact that HE ruined them and HE will still go ahead and eat all the 'good' stuff when I replace it.
We can't tell him to leave, and we can't leave (the house is all tied up in god knows what manner of legal issues so we're all stuck here), but something has to happen, and the best thing I can think of is for BIL to lose control over his own money in favour of DH looking after it, so that whatever NEEDS to be used for bills, can be used for bills, and BIL can have whatever's left to go and get drunk with his mates or do whatever, we don't care.
We don't want to try to rip him off or anything like that, we just want some fairness back in this house, kwim??

If it is possible to change the arrangement at this stage, how do we go about it? What will need to be done in order to change it? Does BIL have to agree to it or can we just go ahead and get it done because he is a minor and under our care, or does Centrelink see him as an adult and allow him to say 'no' to this (because I know he will, he LOVES having $200 a week to blow in the space of two days on whatever the hell he likes, with nobody keeping track of it, he won't like being told he has to give up control of 'his' money)?