Question

approximate bare spherical critical mass condition u-235 required in 50kg an pu 239 required in 10kg

Answer 1

 The factor you pointed out, the average fission neutrons produced does have effect on the critical mass- it should decrease the critical mass a little bit. In a so called "Bare spherical critical mass" condition, U-235 required is 50 kg and Pu-239 required is 10 kg. Both values are approximate and for reactor-grade materials, not weapons grade.