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.
I am not sure scace is the right word.
Strikes me that a lot of soon to be past use by date has gone over and looking at it from a very realpolitik perspective it is a very cheap way of degrading the Russian military, a lot of money but small beer is US military spending terms.
I have not heard of expedited biometrics bit they do not seem to take that long.
Being realistic I suppose relative to how long he has to go they will be back and firmly established in the US long before he is interviewed.
It is not anyone on here that has to be persuaded it is the Consulate.
Noted your Father just wants to visit.
Your Brother is looking at say a 30 year wait so if he goes that route he would be close to retirement presumably.
Of course not, I visited the US quite a few times, and knew nobody in the US, I did not need anyone to approve my visit.
They do not need your permission