Profits coming through the privileged money creation process mainly occurs at the member bank level of operation, and those profits are not turned over to the Treasury.
Member banks do not benefit from seigniorage.
Of course they do. Any stock holding member bank derives a percentage seignorage, it's one of the primary ways they make money. What could endlessly be debated is how much they benefit from seigniorage. Here is an old but good article on the subject.
On a side note have you ever wondered how a non profit organization ends up with more than 2 trillion dollars in assets?