I have some 1/2" thick cherry tongue and groove planks that are all
cut to 36" length and various widths. I want to install them in the
kitchen nook area of my home as wainscoting (floor up to 36" high).
I currently have drywall (floor to ceiling) with cherry baseboard and
chair rail.

My plan is to cut out 36" high of drywall, install 2x4 runners
horizontally between the existing studs near 6" and 30" height to give
me something to nail the T&G cherry to. Then reinstall the chair rail
and baseboard.

How would you install the 2x4 runners? I was thinking flat faced
outward, toe nailed. Or I could stagger them a bit and come in with a
nail straight through the stud and into the end.

I also planned to seal the area by shoving foam or insulation up
between the drywall to prevent air leakage since the T&G won't be air
tight and we run the A/C quite a bit being in Florida. There is a
fire break (2x4) running horizontally about 48" high. Do I even need a
seal with the firebreak there?