Ship Strategy & Fleet Strategy in strategic combat-how does it work?

[MegaTrain]

I played with these strategies in some solo games to see if I can get the hang of them, but I couldn't quite get the result I wanted.

My goal was to come in to an enemy's home sector, wipe out all ships and bases with weapons, but not destroy his home world (so I could get his surrender and use his oxygen-breathing population).

You can set it to NOT fire on planets, but then your ships just sit there and take a pounding from the weapon platform missles from the planet. They don't move away from the planet, even when the secondary strategy is "don't get hurt" and all other targets are destoyed.

If I ALLOW them to fire on planets, then the planet and everything on it will die, no matter what I do. Even if I set it to "Damage until all weapons gone" or set the "Damage percent per planet" to 50%, they always come back to finish them off.

Obviously, the context here is strategic combat, as I can do whatever the heck I want in Tactical. Anything I'm missing? Or is there no way to make it do what I want?