Is 10 cents per page like a good ad performance?

I'm really confused if that's good or not. I have created and tested about 15ads so far this week, running them all for 5$ to see which one performs the best. Surprisingly, my best ad was the first one I've created, getting likes at about 10cents. I have had as bad as 0.75cents likes. My niche is alternative news/paranormal/ufo, that sort stuff.

Few questions:

1.)My best ad was set to show up at a specified time(From 18:00 till 23:30 pacific time). Is this a good idea? Maybe I should run the ad for 24hours /per day to get cheaper likes? Because Yesterday I have tried two copies of the same ad and ran them in two stints, one from 18 till 20:30, other from 20:30 till 23:30, hoping to catch the time when my ad performs the best, but my Cost per like jumped from 10cents from original version of the ad to 25-30cents on the new ones.

2.)How does CPM work? I always thought the broader the audience the cheaper it is to advertise. So I have changed the age from 23-no limit from the original ad to 18-no limit and 0-no limit on my testing ads and CPM skyrocketed from ~0.5 dollars to whooping 2-2.5dollars. I have done the same test with sex, as my original ad only targets men, I've set to target all and my CPM skyrocketed again.

In the end it looks like that I've got lucky to get that ad for 10cents per like, as all my attempts to find a better one fails miserably, even when I go to bed thinking that in the morning I will have a winner I usually wake up and see results screwing my whole day

I would go for the 10cent ad and just invest in it, but I'm not so sure if 10cents is a good cost per like. That's why I would really appreciate some advises on how I could optimize facebook ad and how to understand CPM, because my thinking is flawed, at least that's how it looks like.