I do not know if they can consider well-documented crypto earnings notarized by a lawyer as a source of income. @OP had you tried this approach?
Unfortunately they have "only" scammed $300 according to him, I don't know where he's living but a lawyer is likely to cost him half of this price at least, without any guarantee that Stake will accept it at the end.
They show people winning million dollars and they are scamming me for $300. Maybe those promos and social media posts are fake and big fraud is going on.
As we can see their so called guidelines don't belong to their ToS, and can only be found in their "help" section. They don't seem to be even fixed since they obviously can be updated at anytime without notice by a random guy of their company, not CEO.
On top of that they freely state to "reserve the rights to request any document they might need", that is to say while they take the right to only accept documents mentioned on this extra ToS list, they also take the right to require documents not mentioned on the list.
It must be a joke.