This has now been fixed in 1.21, which is releasing within an hour

Since you haven't responded, I'm guessing this is the error in PBR shaders that you get on OSX, which is now fixed for the coming 1.21 :) Let me know if it still happens in there

Doesn't work how? What happens?

You'd need to do lit particles in that case, but, this place isn't for asking "How do I make a shader like this", please do that in the forums instead :)

Bloom would give you that effect:
http://docs.unity3d.com/Manual/script-Bloom.html

It's hard to say what you want to achieve, but if you want light shafts, that's usually done as a post effect, which is included in Unity's standard assets

Not at the moment, though you can probably hack it in using the code node and making sure the names are the same, or you can make your own offset/scale properties

Rename the gl_en_data variable to something else, like gloss_en_data, wherever it's used in the shader code

Hard to say, but I would guess it's done by sunday

This is a known issue and will be fixed in the next update