retro framing sole plates to subfloor/hardwood
i just ripped some linoleum in my utility area where i plan to move my boiler and water heater alcove. much to my pleasant surprise and hope that's what's hiding below ugly carpet in the rest of the 1st floor, i found beautiful dark hardwood that i estimate to be as old as the house (101 yrs) or at least predate WW2.
i plan to leave some of it exposed in the corridor of the area, on whose one side will be the above mentioned alcove and the other a powder room and a laundry alcove. i do plan to cover it with something in the alcoves/powder room.
Q1: should i just rip the heardwood out in the alcoves/powder room area since it won't be exposed to make it more level once i put appropriate flooring there (tiles or linoleum or whatever is adequate under boiler/water heater) or leave it there?
Q2: if i should leave it, should i at least rip the parts where i wanna set my framing sole plates or can i nail them directly to hardwood?
Q3: what kind of nails should i use for nailing sole plates to subfloor/hardwood? 3" regular framing nails are too big (1.5" of the 2x4 + 3/4" of the subfloor)? i can find 2-3/8" nails for my framing nailer but that will be just a notch too big (by 1/8", what do you think?). or should i just do them manually (no big deal) ?