Bill D--yes, "old-time" is narrower but it could still include everything you listed there. It's not just the tin-pan-alley-esque stuff. At least, it's not around here. (Personally, the New Lost City Ramblers are pushing it for "old time", for me. Too much 1960's folk revival in them.)

Personally, I think "folk" makes very little sense as applied to musical STYLE. It works much better if its used to describe origin, independent of style, influence, or other applicable genre; it could include all the genres that could be considered "folk". (Emmylou Harris is often cited as folk. Stylistically she's in that ambiguous folk/country/gentle rock area, and it seems to me she's been a rather big-name studio artist for a very long time now . . . )