Regarding proof of the Rambam’s positions on matter’s again I am far from qualified to offer opinions however the Rogatchover and other’s who take this view do. If you would like to see “proof” I suggest you see Torah,Chazal,and Sciuence by Rabbi Meiselmann. The book is around 900 pages long and a good portion of it is devoted to the Rambam’s opinion.
Rabbi Meiselmann takes the view that the Rambam was using certain language’s to discuss Torah concepts and he marshals a great deal of proof from the entire gamut of the Rambam’s writing’s.
He also makes apoint of not asking the reader to rely on his “interpetation” of the Rambam, rather he provides the exact word’s of the Rambam whenever qouted, along with where they are taken from.