Replying to Reducing Noise At Night

Alright, well for starters, I'm using a nikon d5300 with a Tamron 17-50 f/2.8. I usually film at 24fps with a shutter speed of 1/50 on a flat profile (so i can color correct easier in post-production).

Whenever I attempt to film at night, I always end up getting really noisy footage. I understand that lighting is crucial. From the research that I have done, I know that it's best to keep as low of a f-stop as possible and that your iso shouldn't go above 1000ish. When I do film, I tend to get ok footage of the foreground but my background (that is comprised mostly of the night sky) is really noisy. How do i fix this? is it just my sensor on the camera?

Also, I run into the problem of riders going out of focus as they ride since I am shooting at a low aperture. If i let less light into the camera and raise my aperture to something like an f/11, how do I keep it so they stay in focus.