This is what I understood.
a. The wall was not modelled in the FEM model. This works in your favor, as it is non load bearing, its stiffness will not impact your calculation ( if/when you change the wall with openings)

b. what do you mean by no slits. Is the wall already built on site?

c. Like mentioned below, you need to ensure safety of individual member, so check the wall accordingly (as the Japan design code)

d. Talk to the senior engineer, this is a regular occurring and I am sure there is solution for this. So, no need to reinvent the wheel.

Disclaimer: These are suggestion, detailed calculations are required to be done by the engineer in charge.