Removing flickering of LED lighting
I sort of have an answer but it may not be one that you like.

I have the same problem in a mobile audio recording truck that I am working on.  The person with whom I am working has tried every combination of every single LED fixture and wall-mount dimmer that was available locally as well as several units purchased online.

All of these have some degree of flicker at the low end of lighting.

My solution is sort of drastic.  I'm going to rip the electronics out of every LED fixture in the control room and install a very-fast-acting PWM constant-current driver inside each fixture.  Then I'm going to use one of the standard PWM LED dimmers that we build and simply supply 12V PWM to each fixture.

I have the freedom to do this - I was worried that flicker might be a problem (past experience) and made sure when wiring the control room that I would be able to isolate those particular lighting runs from the 120 Vac supply and instead use DC.  

My particular case is fairly unique in that I have several hundred Amp Hours worth of 12V battery in the truck's battery compartment from which to draw power.  You would have to find somewhere to install your DC power supply, whatever voltage you want to use.

I have two standard LED PWM frequencies that I use: 977 Hz (1024 us tick rate) &amp; 4 KHz.  Both work well and I have never experienced a flicker problem with either.  I'll probably wind up using the 977 Hz version just to give the constant-current LED drivers a fighting chance of working well.