On thing you can do to speed up the Intersect Faces operation is to limit the amount of geometry you make SketchUp look through. If you select all of the geometry in the column to before selecting Intersect Faces, SketchUp has to look at all of the geometry. Turn on Hidden Geometry and select only the geometry around the split line. Then use Intersect Faces>With Selection.

Here I’ve put a rectangle in the column component where I want to split it.

Then I exploded the subgroups inside that need to be split. Next, with Hidden Geometry turned on, I made a very narrow right to left selection window to avoid selecting any more geometry than I had to select.

The next step would be to right click on it and choose Intersect Faces>With Selected. It’ll still take a little time due to the complex nature of the geometry but it won’t take nearly as long as it would if you make SketchUp look at every face in the model.