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There are number of ways to deal with the walls. First, make sure that you have satisfied the force-demand on the wall. As you have said, ETABS gave you the distribution of reinforcement in the wall. This distribution should satisfy the demand for flexure. For shear, the reinforcement suggested by the ETABS may not be adequate. You need to confirm it by adopting the capacity-based design approach. The requirement of boundary element is there to ensure that your wall does not crush, or reinforcement doesn't buckle, due to compression. For that, ETABS only specifies the region where you need to confine the concrete as per ACI code's direction, which depends on the location of neutral axis. Make sure to confine this region; no extra reinforcement is needed if you have provided the vertical reinforcement suggested by the software. However, in order to satisfy the confinement criteria, you may need to add additional vertical reinforcement and thus you may deviate from the arrangement suggested by the software. This can increase the moment capacity of your wall, and thus the shear demand (Capacity-design approach). There is another approach, simplified one, in which engineer only considers the vertical reinforcement within the boundary region to be effective as far as in-plane moment is concerned. In that case Asfy x moment arm should be equal to in-plane demand of moment. Where d is the moment-arm created by boundary zones on either ends of the wall, and As is the total area of steel in boundary zone.

The first thing that you need to do is to complete manual load check per column location per load case to see if loads are being transferred correctly. You did mention that you get different results when you model, so there is a problem with modelling and load transfer. Do this excercice and report which load cases the results don't match and we can go from there.