Thanks for the responses guys. To address some of the questions/comments:
My mother gave up work almost 30 years ago to become a housewife and raise her children, a job she has excelled at. She is now pushing 60 and for her to go back into the working world... not going to happen.
I still love my dad. He's my father, I wouldn't be here if it wasn't for him, and when money isn't a problem he's a great guy. But on the other hand, he has lied to his family so many times that we just can't trust him anymore. Our house on the Blouberg beachfront that he lost was in both my parents' name; he went behind my mom's back and took out a second bond on that house to fund his friend's company. When the company folded, my dad was bankrupted, and the only way we learned about it was when the Sheriff arrived and attached our belongings to cover some of my dad's debts. If we hadn't sold the house when we did, that would also have been taken from us.
Not to mention that all of the above happened in my Matric year, which was great for my grades. You know how much fun it is to come home to find half your furniture is gone? How difficult it is to sleep, wondering if your bed is going to be gone when you get home the next day?
I still love my dad, but he's betrayed his family too many times. I figure if I owe anyone 18 years of support, it's my mother, who has always been there for my brother and I (and for my dad, regardless of how many times he's f**ked up). When the whole bankruptcy issue broke, she supported the family for months on her credit card. The card was finally suspended due to non-payment when she was trying to buy me medicine for my eczema, which resulted in her having a nervous breakdown and spending 3 days in bed. She's such a strong woman that to see her broken like that...
I don't know what's wrong with my dad. I've tried to get him to go to the doctor to see if he has depression, but he's more interested in reading get-rich-quick books and thinking up ludicrous schemes for making money (his latest idea is that Google AdWords will make him rich - of course he won't say how). I have literally tried as hard as I can - we all have - and he just won't change, so the rest of the family has to.
Sounds like a lot of lies and deciet here, sorry to hear you going through all this. My father had a gambling addiction and many of these things are flashing red lights in my head. I must say that in many ways I agree in principle with what you did, but there is a bit more tact that could have been applied to the situation. Also some realizations you need to come to on the reality of your situation.
For instance, your mother would have only had a credit card by virtue of your fathers income. The banks could not have given her a credit card without an income so she is not really a hero for keeping the boat afloat with the credit card. Its the same things as pawning your belongings really, Its money that you dont have and is actually making the situation worse once you cap it and start getting charged interest and blacklisted etc... Which closes of other options for you that may have helped you get out of trouble.
If anything your mother was providing a false sense of security to the whole family which did far more harm than good. Now it is obvious that you love your mother very much, and maybe she thought she was doing the right thing. I am certainly not trying to belittle her, I just think you need to put it all into perspective here. You favour your mother because she walked you to pre-school, made your lunches, was home to help with homework, talk to you, bond with you etc... That whole lifestyle that you praise your mother for was totally provided by your fathers "Absence". Yes your mother might be an amazing woman, and a strong one, but I think you are perhaps biasing too much praise in her direction because she was afforded the opportunity by your dad to nurture you all day. And yes your father screwed up big time by the end, it still doesn't change the fact that he was the only source of income that kept you and your family alive, that must count for something.
I know that after so many years of lies and deciet it is really hard to step back and look at the whole picture without any bias or emotion, but I would suggest taking the time to do so. All this being said, I do believe that you did the right thing in a way. Perhaps your father is a lost cause. But perhaps you can work with him instead of against him. While his dignity is broken its much easier to be led in a direction than it is to be pushed.
I think that the advice by someone earlier in the thread is a good idea. Try applying for a CC and getting your father to do bookkeeping part time, or helping people with tax returns. He evidently must be quite good at hiding finances etc if he managed to keep a household going and had a gambling problem on the side.

Sorry maybe that was ill-timed humour. If you control the company and all the money is paid directly to your bank account instead of to him, you can manage the money. Give him an allowance that depends on how much income he brings in. This would probably work best once he has had a fright from the current situation. Then he will be more willing to accomodate this type of idea.
Last bit of advice for anyone ever thinking of getting married. You owe it to yourself and your future family to never ever ever ever get married CoP (Community of Property). In CoP the sheriff can come and attach property etc... to pay for debts. Even if it's one persons personal/business debt and both their names are on the bond. Its seen as joint. Always marry ANC (with or without acrual depending on your preferences) As the sheriff can never attach a house in both parties names if one of the persons has a business that goes under etc... This way you can take a chance on opening your own business without screwing over your family if it goes under.