I hate to say this, but as it is they've already thrown you a
bone by charging interest only after you graduate.
I know it sucks, but that's the way it has to be. I know what it
feels like. I'm currently taking two loans totalling 100% of my
tuition fees. My parents don't give me any pocket money at all; I
give tuition three times a week to support myself. By the time I
graduate, I'll have total liabilities on the order of around
$25,000.
When NUS increased their tuition fees for two years in a row, you
know that I made a huge amount of noise.
All I can say is to approach the school financial counsellors who
ought to be able to work out some sort of financial aid for you.
With both parents jobless and a large number of dependents in the
household, your sister ought to be eligible for some financial
aid.
If all else fails, take out a loan. It sucks, but the suckier thing
is to have to worry over money while studying.