As I have explained in the question time after the examination, there is a critial correction about the long-range correction of pressure calculation.
As in the assignment of the report, the long-range correction was not included in pressure calculation with press.exe. And, the long-range correction was to be done by yourself. Then, you may think the cut-off radius rc should be 2.5 sigma as in periodic.dat used for periodic2.exe calculation. However, if you investigate the pressure calculation program press.for, you will find that the cut-off radius for the calculation of pressure was not as described as in periodic.dat. The press.for use the cut-off radius of half of box size so that you can more efficiently calculate the pressure. Then, the long-range correction for pressure you need to give must be the half of the box size.
I am sorry for not explaining the above point. Some of students have done simulations with large box size and found that they can get better agreement without the long-range correction. This was because the long-range correction should be very small with the large cut-off radius.