1)
The low-energy correction parameters improve the threshold behaviour 
for (gamma,pi0) and (e,e'pi0) reactions. 
Values of 1.0 give E0+ and L0+ (S0+) multipoles close to the
predictions of chiral perturbation theory.

2)
The PS-PV mixing parameter can change the cut-off parameter Lambda_m 
relativ to its standard value 450 MeV, see Eq. (12) of D. Drechsel, 
O. Hanstein, S.S. Kamalov, L. Tiator, Nucl. Phys. A 645 (1999) 145.

a value of 0 will give a pure PS coupling
a value of 1000 or more will give a pure PV coupling
all values in between result in PS-PV mixing in accordance with Eq. (12)

The recommended (standard) value is 1.0
Even in this case the coupling is practically PV in the threshold region.  

Note: This mixing parameter changes only E0+,L0+,M1- and L1- partial waves.