Cloudy water is common in new tanks. As the beneficial bacteria starts to form, you will get a bacterial bloom which will turn the water somewhat cloudy. That isn't a problem. It will clear up once the tank has finished cycling. I would beware of doing 70% water changes except in emergencies or unless you are fishless cycling. Water changes that large can greatly alter your pH and have deadly effects on your fish. As others have suggested, stick with 20 to 25 percent weekly.
As for vacuuming, get a small gravel vacuum. It will suck just as much up but doesn't take water out quite so fast. If I use my large vacuum, it will take out 5 gallon in just a couple minutes but the small one takes 5 to 10 minutes so I have plenty of time to vacuum the entire tank. Once you get the tank vacuumed with the small one, you can switch to the large one if you want to speed things up. I always use the small one on my 29 gallon tank.