For what it's worth as parents I really feel if we can't help our children - regardless of the finances.. it's a poor show. I get "teaching a lesson" for the blow out of money..but seriously the undervalue of your car? that's just plain mean..your dad could have handled it so much better, maybe lending you the money with a strict payment plan and hold the car as collateral rather than the extreme action he took. We have all made poor choices and errors with money.
I think you feel bitter because you are still struggling for money and don't feel they are helping you. If I was you, I wouldn't give any information at all regarding you lack of finances.
Now, the tough part.. Put on your big girl pants and forget your parent's finances, your dad didn't take a "present" back..he sold your car to sort out your debt. ( regardless of his fianancial state). Pride yourself in being independent, you are working hard and managing all by yourself with your toddler. A great achievement. Stop thinking about their money and how they should give you some to help you out.
Have you considered your parents may feel you always just want money from them? whether you ask or not, just the fact you imply and mention to them about your money woes? it's not a nice feeling thinking people only want to bother with you to extract money - regardless if you can afford it or not.
If you want a relationship with your parents..try and see them without any mention of money/finances, and enjoy their company, most of all, you will have yourself pride and respect kept in tact.
I know it's hard studying with children, I have just finished my dissertation after 4yrs study and I have 3 DD's..it's been really hard, working and studying and looking after the family.
But it can be done..and you are doing it, being bitter will not help you at all. let it go and take responsibility for yourself, we all make choices and have to live with them.
Your relationship with your parents may well improve..for the record I do think it's harsh, however you have to respect their choice and not allow yourself to be embittered.
I really wish you luck in your studies.. :)