Staad Pro analysis of moment connection

Hi all,

I have a steel frame with moment connections and pinned connections. At the top of one column (which is a moment connection) I have three beams with the following forces and moments (for ultimate limit state):

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 The column is member no 6,  beam no. 106 is pinned to the column and beam numbers 114 and 309 have moment connections to the column. 

Both beams 114 and 309 are IPE270s and the column is a HE160A.

We advised our fabricator of the following maximum forces and moments for the design of the connections of the IPE270s to the column:

Fx = 5kN, Fy =82kN, Fz = 3kN,  Mx = 0, My = 0.2kNm and Mz = 80kNm

Our fabricator came back and said 80kNm is greater than the capacity of the column in the z axis and that there is additional moment coming in to the column from the adjoining beam (-52.597kNm). And he is right the capacity of this HEA160 column is 57.6kNm.

But then when I analyse this column I get the following results (for Ultimate limit state):

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 Which shows the column passing with a utility ration of 0.75, the capacity of the column is 57.6kNm and the critical Mz moment is -28.11kNm.

So my questions are:

1. Were we correct in advising the fabricator that the maximum Mz for the beam connections design is 80kNm?
2. Presumably Staad carried out moment distribution at the joint/node (no. 74) and distributed the moments between them members according to their stiffness to get equilibrium? Sum of the moments at this node is: -28.112 + 79.466 - 52.597 = -1.243, which is close to zero but not quite.
3. Is it correct that the actual Mz moment that the column has to support is -28.11kNm and not 80kNm or greater? Presumably the +79.4kNm from one beam is counter balanced by the -52.5kNm from the other beam giving a net moment of 26.9kNm? Which is close to the value of 28.112kNm that staad gives for the column.
4. And that both beams are designed for a connection onto the column of 80kNm but that the column itself only has to support 28.11kNm?
5. Should the fabricator design the column/beam connection with stiffeners locally to absorb the greater 80kNm on both sides of the column?
6. Presumably when staad states that the capacity of the column is 57.6kNm that that is the capacity of the column at its mid height and not at the top of the column where it is much stiffer?

I will send on the staad file if necessary, doesn't seem to be a facility here for attaching it.

Any help here would be much appreciated.

thanks.