Here is my process in RawTherapee:
We start in the Raw tab. The first thing I notice is that you have horizontal banding. RawTherapee can deal with this using the "Line noise filter". Set the direction to "horizontal" and the value to something that seems to work (around 400). Note: this is not perfect, there is some residual banding. I think you'd need to take some darks to get rid of it completely.
The next step is to adjust the demosaicing. For noisy images, IGV is probably the best option, pumping "False color suppression steps" to 5.
Moving on to the noise tab, you can start with "Impulse noise reduction", which will take care of the "salt and pepper" noise. Then, on "Noise reduction", set the colour space to
L*a*b, since you want it to work in luminance, and the mode to Aggressive, since there is plenty of noise to go around. Adjust the luminance slider to taste. You can also turn on the median filter, that will clean up a lot of what it is left. In my opinion, the best is the window of 5x5 soft, with 3 iterations. Remember, this only shows if you are zoomed in at 100% or more.
The next step is to turn the image black and white, because the colour is just noise. You can do that on the colour tab.
Finally, you can bring back some of the "pop" in the original image without raising the noise playing with Retinex and Haze removal.
Some of these steps are a bit computationally intensive, specially the last one, so if you have an old computer it may be a bit slow to find the right settings for you. A tip is to set the demosaicing algorithm in the settings to "fast" for lower zooms. This will speed up when you are tuning "global" settings, such as the white balance or the overall contrast, but will use the slower method when you are likely to see differences, ie, when you are zoomed in.
Whole (with a lot of JPEG compression, sorry):