My moon won't orbit my planet, and why can't I change the density?

[ahoop]

I had a moon before, but it was perfect until something I did screwed it up. I deleted it, placed another, set its orbital period, and then it went way further from the planet than it should. I showed its orbit and found it orbiting the star instead -_-. It keeps happening.

I'm also trying to make any new moons the same as the very first one, but I can't have the radius and mass the same without changing the density, but it keeps locking.

[C7]

Mass, radius and Density are interlinked values. If you have a specific density, and mass, it will define the radius of an object. As well, the inverse is true, if you adjust the radius, you will by definition change the density.

The orbit lines are drawn as the body is moving, not necessarily in relation to what it's orbiting. So if you place a moon down, as a planet is going around the sun, it will draw a corkscrew line. It's just a matter of visualization, the orbits should be the same. Just in case, be sure you check the placement method you're using, and that it's selected "orbit", and not still, or another method.