I can imagine any pro photographers grinding their teeth at a lot of the above, because focal point / focus distance has nothing to do with the f-stop.

The focal point is where a desired point in the subject is in sharpest focus at the object, the subject being the scene, the object being the image plane (e.g. the camera film or sensor).

It's what you focused on.

Strictly speaking, it doesn't produce a point at the object but a circle, which is referred to as the 'blur circle' or 'circle of confusion'.

The size of this blur circle is determined by the aperture (f-stop) through which light passes; as the aperture becomes smaller, so does the blur circle. This means that reducing the size of the aperture increases the range of the subject's depth (Z-plane in 3D-speak) that appears to be in sharp focus. It increases the depth of field.

I have to stress this: what you focus on and the size of the hole in your lens are not related. 

Poser - and other 3D apps - attempt to simulate the depth-of-field effect but I've yet to find one that does it really well, and in Poser you'll need to (a) crank up your render settings and (b) endure very long render times to get anything acceptable.

A far quicker, more controllable method is to render out a depth-map (Z-plane map), and apply depth-of-field effects in post processing.

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Windows 10 x64 Pro - Intel Xeon E5450 @ 3.00GHz (x2)

PoserPro 11 - Units: Metres

Adobe CC 2017