First here are some modifications to the units used in your formulas.  Use standard metric units to be sure you get answers without conversion factors, see the following:
 
Flow capacity: Q = C1 x n x D2 x S

Power required: P = C2 x r x n3 x D5

Q = Agitator flow (m3/s)
P = Power (W)
n = Revolution speed (rps)
D = Propeller diameter (m)
S = Propeller pitch
r = Density (Kg/m3)
C1 = Factor specific for the propeller
C2 = Factor depending on turbulence
 
Then for different propeller pitches, use the following values for C1 and C2
S = 1.0    C1 = 0.54    C2 = 0.35
S = 1.5    C1 = 0.66    C2 = 0.62
S = 2.0    C1 = 0.77    C2 = 1.00
S = 2.5    C1 = 0.85    C2 = 1.35