Tip: Zoom in so the nodes and information is readable when exporting the workspace, Dynamo will use the whole graph.
Your graph is creating new elements
Some notes
You were missing surfaces where the slope was greater that 0.5 (z < 0.5). You can get all where Z is positive and greater than 0
Turn off previews and use coloured geometry to help visualise. Use bounding box max and min for the lines
Graph modify the existing Revit families (see full graph below)
Revised graph
