What type of bonds were given by your grandparents? Government, corporate, municipal, other ... How was your stepfather able to cash in a piece of paper with your name on it and a time limit before it could be cashed in?
Your car is in good shape. Keep it. It is a good asset. You will need it to travel to school and to summer jobs. Good luck getting anywhere without it in this society of personal transportation.
It sounds like you are/were pretty affluent, yet the rest of your family has no concern for helping to finance your education? That does not make sense.
The rest of your family was not watching this man control these finances?
Your mom gave financial control of her and her child's assets to a second spouse? Second spouses are rarely known for much time before a divorcee jumps into a permanent relationship. I would think any reasonable person would retain control of their own assets after going through a divorce. That is just normal self-preservation. (I assume parents went through divorce due to having both a step-mom and a step-dad.)
You family seems to be surrounded by people taking advantage of you. i.e. your stepdad and stepmom. Where is the common sense to prevent this? Why are these strangers being given free reign to family assets. Something is seriously wrong here.
I call shens on this thread.
Public schools require a FAFSA. Private schools are not required to use a FAFSA and have their own methods of determining financial aid that may be of benefit to you in this situation. Try talking to financial aid counselors, both public and private, to see if you can change your status to independent. They are probably calculating financial aid for next year right now. This is the time to talk to them.
Are you sure the stepfather "lost" the money or did he transfer it elsewhere outside of your knowledge? Maybe you can sue him for financial irresponsibility. It seems it is time for you to become financially independent.
The military provides the GI Bill and other financial college incentives. Often individual states will pay for educational expenses for returning veterans.
Get a job during the summer, and take loans during the school semester. Preferably government subsized loans.
Study and earn scholarships.
Move out of your rented house and find a roommate to share an apartment with.
It is time for you to grow up and gain control of your life. It seems you will have to work like the rest of us now. There really is little problem, assuming you still have your health, mind, and the ability to complete your education. You can get financial aid in some form, even loans, to complete your education. Then you can pay it all off with your new job after graduation.
This seems workable to me.
Edit:
How did you file your FAFSA for next year if you have known about this situation for 5 months already? You should have already taken care of your financial aid problem when you properly filled out the FAFSA form at tax time with the information you were aware of. You should have been asking these questions two months ago.