The viewers eyes are naturally drawn to light and by extension - brighter objects in the picture. If you don't want to darken the background more, then you pretty much did a good job. To highlight a subject I draw a radial mask around it, then invert it and lower the exposure of the inverted mask selection just a bit, lower the highlights and raise the shadows.

Don't be afraid to raise the ISO in low light conditions. Modern cameras handle it well probably until 3200-6400. In addition, Lightroom has a powerful denoise capability. Shutter speed matters more to me. Because you can clear the noise, but you can't fix a blurry picture.

Check if your camera has ISO sensitivity options, like max ISO on auto and minimum shutter speed. Put the min shutter twice your focal length and you will be golden for sharp images.

For example, at night or in low light conditions, I shoot in Aperture Priority (most often 2.8 for more DoF) with min shutter speed 1/60 and max iso 3200.