Here are my thoughts on your questions:
(1) An inflation of prices would occur as a result of monetizing silver. It would be the same effect as a sudden, massive discovery of gold.
(2) Yes, presumably Foner has in mind the federal government’s lack of interest in Greenback or silver schemes.
(3) Foner is way off here, if we’re not taking him out of context. Homestead did not become nonunion until after the strike. The strike was about wages. I recommend the article by Charles Baird, linked on the Populism lecture page.