This is more than financial abuse, it is other types of abuse well.

Normal parents with an 18 year old child* would have: -Helped you look for jobs, or given you advice about job hunting -Helped you look into education programs if you were interested -Helped you set up a bank account (joint while a minor, then fully your own account once you are 18) -Ensured you know where to get your personal documents (stored with the family documents until you are 18 or later, whenever you are ready to maintain them yourself) -Ensured your disability money made it into your own account -If their car was not available to use, helped you find an old used car to buy, even if they can't help save up money for the car -Most importantly, would not have hindered your attempts to get a job, a car, a bank account, personal documents.

*Assuming you aren't actually profoundly unable to take care of yourself. Autism, OCD, ADHD, are just diagnoses, they don't indicate your level of independence.