how can i shoot moving objects at night without bluring
Open your cameras flash, and in the menus find your Flash mode settings. Set your camera to "Rear" or "Rear Sync" or "Rear Curtain" flash.
Then shoot your subject.
What does this do? It fires your flash just before the shutter closes which will capture your subject as it is in action.
If it is a car, or anything with a light, it will look something like this
Also for your DPI question, you could just shoot RAW. That should be something around 240dpi. The other option would be to just up the resolution during post-processing when you crop.