Sorry this reply has taken so long.  I managed to lose the first version of it and had to rewrite it.

Hmmmmmmmm.  Yes, I do see the white spots, and no I don't know what's causing it.  It looks like very small and bright specular, but that equation should never give you specular that small.

I'm also stumped by your light color issues.  I never mess with diffuse or specular colors on lights, so mine are always default white.  I just color the light.  I would expect your lights to get nice and saturated by this.  

I made that image ages ago (Poser 6, IIRC), so I don't exactly use the same techniques now.  That said, the basic principles of my lighting have been pretty constant.  

I always start with a notion of what's happening in my scene, both on and off camera.  I make my lights match the real world scene in my head as much as I can.  This currently means using raytraced shadows.  I use a blur from 1 to 15 or so depending on what type of light I'm making.  My shadow bias is as low as I can get away with. I usually start with 0.2 and see how it goes.  My shadow samples are always higher than 32.  I've gone as high as 128, and I usually use 64. For spots I might use inverse square or linear falloff, and for points I use inverse squared falloff.

For environment lighting, I use IBL or an environment mesh with an emiting material.  If I use an IBL, I have to come up with a way to add the IBL's image to reflections.  If I use an environment mesh, I often have to come up with a way for something else to show in the background, because such a tiny portion of it shows that even a 5000+ px texture for the whole mesh isn't large enough to render well.  If I'm using the environment mesh to give windows or doors or other portals light, then I might boost the ambient value up higher than 1.  

As far as I can tell, the whole "fill" light element of 3 pt lighting comes from before GI and IBL.   I remember the old 3 point light tutorials, and the fill light always imitated bounced or indirect light.  I never use a directional "fill" light.  And I've always tried to match my environment lighting to my scene.

My directional lighting depends on my type of scene.

If it's an indoor studio scene, I usually have a main and accent light, though I might just use a main light.  I used to use spots for those, but now I use my own custom softboxes.  They're a combination of emitting props and point lights that I use as one light.  I'll eventually sell them as part of my photo studio set, but I'll need to stop using it and get back to packaging it.

If it's a candid indoor or outdoor night scene, then I light to match the elements of the scene that emit light.  I use single point lights for lamps, torches, candles, and glowing single glowing objects.  I use more than one for fires and large or long glowing objects.  The softer the light the source should cast (basically, the more diffused the light is), the greater the blur I put on the light.

For natural light, I always use a single infinite with very low blur.  Moonlight is hugely less bright than sun, and sunlight is strongest in the yellow spectrum.

The only really tricky thing I've learned is to watch what point lights are close to.  They seem to have a bug that gives them a weird hard shadow on anything that comes too close.