New pool owner, general maintenance questions.

I live in east central FL, have a 10k gallon concrete in ground pool, serviced by a Pure Chlor salt system. There is not a screen enclosure around the pool and there are no trees within approximately 200' of the pool. My questions follow: During the off season and high use seasons how long should I allow the pool pump to run? Again, considering the seasons, how long should I allow the Creepy Krawly to operate? Considering the seasons and taking into account there is a pressure gauge on the filter housing how often should I clean/replace the filter as I do not trust the gauge? Finally, considering the seasons, what chemicals are in fact essential to healthy maintenance of the pool? I have my water tested bi-weekly by a local pool supply store but I want to ensure they are not selling me things I do not need based upon the water analysis. Thank you in advance for your assistance.