I had a look at your model. Running a 3D-FEM analysis is
an overkill of work and not necessary. It is much easier to use
a frame program for such a problem
Your load case uses only vertical loading near by the knots of the structure.
The (static relevant) bending-moment in the beams is nearly zero, the load directly
runs into the columns. The complete structure will tilt, you must use anchors
at the floor (or more selfweight).
You can divide the 3D-structure into several 2D-subproblems (the yellow frame
for instance). Critical loading is horizontal / diagonal.