That is not gonna prevent you from running into the issue I've mentioned before. But yes, all the ornaments and non blocking geometry should be func_detail. The reason for that is that source engine uses binary space partitioning as an occulusion culling method. It needs to generate the series of rooms and all the ornaments would create too much splits thus make ur vis-leaf graph very complex.
Here is the link to a good video talking about binary space partitioning if you are interested, it's more from a programmers point of view but still very interesting.
The reason why the vertex count for all the brushes on the map is 65k is that all vertices get put into one big vertex buffer. To later draw it you use index buffers. Source engine uses 16bit integers for that, so the maximal number of vertices you can have in your vertex buffer is 2^16.
Edit: Each model is loaded into separate vertex buffer (sometimes can be combined to minimize gpu calls), so you can have more than 2^16 in your sceen at the time.