1. I added the 3 guppies and 2 mollies two days ago. The readings are still at 0 but the water has turned a little cloudy. Just wondering if this is something I should be concerned about? If it's a bacterial bloom, which is often seen in new tanks, it is a sign of ammonia. Are you still taking water to the LFS for testing, or do you have your own test kit?
2. Is my tank going to cycle again? Every time you add fish, you increase the amount of work the filter bacteria have to do - they then need to grow a larger colony in order to cope. You will probably see a small ammonia and nitrite spike, which you should deal with by increased water changes. I would suggest you test daily, to monitor the situation.
3. Also, once the cycle is complete how often should I be doing regular water changes? (everyone tells me different things) I change water in my tanks weekly, by about 30%. Ensure while you are doing these changes that you clear the substrate of any debris, etc.
4. How much should I be feeding 8 guppies and 2 mollies (flake food) Feed them once a day, and feed them very sparingly, give them only 1 minute's worth of food, if that. Their stomachs are only as big as their eyes, and they have no mechanism to tell them that they are full. It is so easy to overfeed, and this can cause further problems. Many people recommend only feeding 6 days per week.