The RMF is probably the models importer. Game data files, probably the data files for Half life binaries etc etc. idk about the other stuff… Are those settings you need to “set” in order for it to work, or are they “chooseable” ?
RMF is the predecessor of VMF, so that’s the directory where your map source files are located.
The FGD/Game Data File contains information about the used entities. It’s normally located in the main directory of the mod you’re mapping for. In case of Valves games, yeah, they might be located in the according GCF. There are custom FGDs (google) with fixed/extended entity funtions around.
Textures are packaged in WAD files., also usually located in the mods main directory.
Oh and if you’re really intending to create maps for HL1, you should get Zoners custom compile tools and use them instead of the native valve tools, as those are outdated.