If andlord is refusing to return security deposit of developmentally disabled long term tenant because we only gave 30 day notice, what can I do?

The landlord does not know the law. A tenant never has to give more than 30 days notice. If the person has been there for a year or more, the landlord must give a 60 day notice, but the tenant still has to give only 30 days. ?Point out that the landlord has only 21 days to return the security deposit. Before you tell the landlord his error, get him to commit himself that the only reason for withholding the funds is lack of notice, as otherwise he will come up with a different reason. If it has been close to 21 days, wait until that time has passed so that he can not raise another issue

The landlord must give you 60 days notice to terminate, but that is not necessarily the time the tenant needs to give the landlord. Consult the lease.