You have asked for specific answers and provide no information.
Generally I look at an EB5 as buying a Green Card any money you get back is a bonus. He must have applied sometime ago through a regional scheme with that amount. You do not even mention the scheme.
You mention you have a Lawyer who presumably have perused the terms of the agreement, there are exit clauses and I would think it very unlikely your Uncle would have invested without both legal and financial advice so I would start by contacting those advisers.