Cannot remove city glow from "bottom right" of astro image

Here's another approach.

With the Eyedropper tool, sample a dark area of the image, for example in the upper left.

Add a new layer underneath the original layer. Fill that layer with the dark color that you sampled.

Double click on the right side of the top layer to bring up the Layer Style panel. Move the shadow slider for This Layer to the right. For a smoother transition, hold down Alt or Option to split the slider. Adjust the left and right sides of the split slider until the white dots show the way you want.

One thing to try is to duplicate the layer and set it to Multiply. I did that below. You can then play with the opacity of the top layer (I left it at 100% here, which is why it looks very dark). Having said that, the image does have some lens vignetting in the corners, which you can try minimizing by erasing the darker areas (on the "Multiply" layer). 

-edit-  The screenshot here looks black, but IRL you can see the stars. Just adjust the opacity and contrast.with a large soft brush at a lowered opacity. (Make a copy of the duplicated ater first) Also try adjusting the Contrast.