Rust can burn, mix it with aluminium to make poor man's thermite (do not try this inside or near anything flammable it burns at a very high temp and can melt steel containers). And, yes I know all about Fe2O3, Fe3O4, FeO, etc.
That still does not address any of the issues I asked about.
I`m not telling you not to do this as I don`t have concrete evidence either way.
What I did say is, without concrete evidence that it is safe I wouldn`t suggest people expose their reptiles to it.