The odd number of times is to try to prevent the eggs being mostly in one position. You need to look at your schedule to see what works best for you. Overnight is one possible long time but if you are gone to work during the day, you may need to work it out so that is different from nighttime. It is hard to say what works best for everyone. But more is generally better than less.
I'm not going into the detail Pete did, mainly because I cannot, but inadequate turning can cause even more problems, including malformed chicks. It's not that these problems develop each and every time without fail, but that improper turning can cause some to have problems. Those chicks can be pretty tough and in spite of us doing a lot of things wrong, sometimes they make it anyway. But your odds of success are much better if you can do more things "right".
About the temperatures. The thing that mostly matters is average incubating temperatures. As long as it does not get high enough or low enough to affect the core temperatures of the eggs, they should hatch OK. If the average incubating temperatures are low, they will probably hatch a little late, maybe a couple of days. If it is too warm, they will probably hatch early. With that temperature range, you will probably be OK. It might help stabilize the temperature if you can add a thermal mass. What I would suggest is adding a zip loc type bag full of water. Once it reaches the right temperature, it will help stabilize the temperature swings. It should not be a fatal flaw if it varies that much, but it would obviously be better if you could narrow that range down. It's another one of those things where your odds are better if you can get it closer to right.
Good luck!