If you’re using Particular then you can link a Light to your first Null, name the light Emitter and select that as the partiocle emitter in Particular.
If I understand you correctly, I would suggest precomposing everything and then Time Remapping the Precomp. This will allow you to set keyframes where you want to adjust the speed and move them around to get the desired effect.
You can get really nice and fast results with ShapeShifter AE even without Elementary- use a reflection map, work at 32 bit and apply a soft Glow on the highlights and you’ll get nice shiny text.
I was suggesting a different angle for the mirror- one where you eliminate the reflection of the actor and introduce the reflection of the lamp and the wall – I think that will make it more believable. Create a Null using the track points (camera track) from the mirror frame and position the lamp and the wall in 3d behind that Null in Zspace to create the correct perspective change.
Give us a bit more info- what are your settings: color space, 8,16 or 32 bit, color profile and AE version. Posting a couple of stills to illustrate the issue could help.
There are quite a few folks out there looking and asking for the same or similar feature- make sure you submit this to Adobe, they have the good habit of listening to their users.