A Joule is equal to one newton-meter (or metre if you're so inclined). Force times distance.
Foot-pounds are the same: Force times distance (well, distance times force). The confusion comes from pound in this case referring to "pound-force" or lbf, a unit equal to one pound times g.
J/kg is a different measure, the specific kinetic energy of an object; the amount of energy per unit mass. The imperial equivalent would be ft*lbf / lb (foot * pound-force / pound)
Metric: J/kg = N*m/kg = (kg * m/s^2 * m)/kg = m/s^2 * m = m^2/s^2
Imperial: lbf*ft/lb = lb*g*ft/lb = g*ft = ~32.174 * ft/s^2 * ft = ~32.174*ft^2/s^2
As you can see, the choice of g rather than 1 ft/s^2 was unfortunate, but otherwise the systems are equivalent.