I am trying to use a grain mill for peanut butter, and also pureeing vegetables. Can this work?
Don't do it.
a] it won't work properly &
b] you'll ruin the machine. It is supposed to take bone-dry grain in the top, grind between two flat(ish) granite plates - actual millstones - & pour fresh-milled flour out of a spout. It will not only clog the mechanism & not pour through, it will ruin the millstones by getting them greasy &/or wet.
Don't ruin a €600 mill trying to do a job you could get a dedicated machine for €35 to do better.