I don't have any particular information about a situation like yours, and I am not an attorney (although I did score very well on the LSAT several decades ago...I trust you understand this is tongue in cheek - don't take any of my hunches/suggestions as legal advice) but I've had my run-in's with my own SSDI status over the years (was on then off then on again with lots of aggro, although less than most).

You're likely familiar with this pamphlet: https://www.ssa.gov/pubs/EN-05-10026.pdf

It says this near the beginning:

...for adults who became disabled
in childhood (prior to age 22), and who
might be entitled to Social Security
Disability Insurance (SSDI) benefits.
(We call this SSDI benefit a “child’s”
benefit because it’s paid on a parent’s
Social Security earnings record.)

So, I believe this differentiates between survivor benefits and disability benefits for children of workers (it would appear that the parents can be either live or deceased).

Here's what little I know from reading your essays:
1) you were previously considered disabled as a child by Social Security.
It appears to me that you would have received SSI benefits as a child (more on SSI below a ways).
2) your benefits where switched from disability benefits to survivor benefits which then expired when you aged-out. Survivor benefits are attached to your parent's employment. There are ALSO, it appears, disability benefits attached to a parent's employment if an employee's child is determined to be disabled while still a child - this is a DIFFERENT benefit, and I'm guessing still may be available to you.

If that is correct, it would appear you are already established in the system as having been disabled as a child, which *should* make you eligible for disability insurance under your father's (and perhaps mother's if she worked as well) work. It may be that you were switched because the survivor benefits were more generous than what you were receiving as childhood benefits and that one can receive one or the other but not both simultaneously. Maybe the concept was that you would be switched to disability benefits through your parent's account once the survivor benefits expired. I'm not sure if there are different pots of money. This may have been a smart move - I'm sure you'll figure that out in time regardless of how it appears currently.

Getting an attorney might be helpful, but then you'll end up owing a chunk of your benefits to that person, and like anyone in this situation, I'm sure you likely have need of that money for your preservation. At any rate, I'd see what sort of assistance is available for you without charge before hiring an attorney. If you do eventually need to hire one, perhaps you can negotiate a reduced fee since you've done some of the legwork yourself.

Here's the first place I would check for assistance - there should be a constituent services person at your Congressperson's office dedicated to assisting constituents on matters of federal benefits. Make an appointment to meet with this person. Bring your Social Security card if you have it and your photo ID.

There are some organizations around the country which assist folks with Autism Spectrum issues to assist in navigating difficult social situations. If there is a service like this in your area, I would ask for an assistant to go with you for this appointment. If this service is available in your area, they may be able to help with the whole process as your advocate.

Easterseals has a program like this: http://www.easterseals.com/our-programs/autism-services/?referrer=https:...

I don't know if this guide gives information about services in your state: https://www.medicaid.gov/Medicaid-CHIP-Program-Information/By-Topics/Lon...

For the meeting with the Congressional office staffer, first thing you need that person to track down is the childhood determination that you were disabled. Get a copy of it for your records.

Second thing you need them to track down is what the switch is which transpired when you were 12. Have them get the paperwork on it for your records. Have them explain to you what that change meant including any explanation of whether that altered the earlier determination.

You'll need to know those two things before your proceed.

Don't feel funny asking for help - the congressional office does this sort of thing for many, many people.

SSI Supplement Security Income is different from SSDI Social Security Disability Income. The latter is a form of insurance which workers pay into with each paycheck.

Have hope. There really *should* in this day and age be folks out there who can assist you with obtaining benefits. Feel free to message me, although I'm no pro in this area.

If you *do* qualify for SSDI under your parents' account(s), there may be back payments for you.