Your second post is basically correct, but watch the units.... Below are the conventions used for calculating the Df and Cd....

Distances are in feet

Frontal Area is in ft^2 = in^2 / 144

Velocities are in feet/sec

Time is in seconds

Acceleration is in feet/sec^2

Drag Force is in lbs.

Mass is in slugs = lbs / 32.174 = grains / 225218 .... (your 225120 is close enough)

Air Density is in slugs/ft^3 = lb/ft^3 / 32.174 .... (you can look up air density in lb/ft^3 for your altitude, barometric pressure, and humidity)

Cd is a dimensionless number, as is the Cg, so therefore FF is also dimensionless....

SD is calculated from (grains / 7000) / cal^2.... where in this case the weight in grains is converted to lbs., and the caliber is in inches.... The units are "sort of" psi, but since the factor PI/4 is not used, the SD in ballistics is considered dimensionless.... so the BC ends up dimensionless also....

HTHs....

Bob