As far as state assistance/programs for disabled adults go, Florida ranks near the bottom nationally. I would NOT move to Florida. Its possibly worse than Montana.
We live in CA, in Orange County. It costs an arm and a leg to live here, but this state and in particular this county, has a VERY good, established program through Regional Center in partnership with hundreds of local and national businesses to provide work programs for disabled adults. Our 2 sons are autistic and will likely work through these programs when they graduate HS as well.
Disneyland is, for sure, a partner in this program. They hire bus boys that work in a couple of the Disneyland quick service locations, clearing trays, mopping floors, wiping down tables. I have seen these employees numerous times over the years. They also work with large supermarket chains and hire baggers, cart retrievers, etc. Starbucks is also part of the program, as are many other companies.
If you can literally move anywhere (income/jobs allow that), look for a place with well established work programs for disabled adults, without years long waiting lists. Massachusetts is supposed to be very good in this area, as is Minnesota. Most southern states are terrible. Texas has a good reputation as well, as does Arizona. California is good, but supposedly Oregon and Washington aren't so good. Colorado is also supposedly good. You can Google "best places to live for disabled adults" and look for the index that measures work opportunities.
Your narrow focus on getting your son a job at WDW is not the best way to go. However, if you truly feel that where you are won't help your son reach his full potential, moving somewhere that will isn't crazy.