I'm going to take this a little at a time-- there is too much
here for me to chew on at one time.

If you're interested in Good vs. Evil, there are two main religions you
might want to look at. The first is Zoroastrianism.

The second is Manichaeism. Mani developed a religion closely associated
with Gnosticism, and this is from the Britannica: "In the beginning,
then, there were two antagonistic substances, the one absolutely good,
the other radically evil-- Light and Darkness. Both were uncreated,
eternal, and equal, each one living in a separate region..." Then
Darkness attempted to invade the kingdom of Light. Read up on these two
and see what you get.

> Perhaps God is "all good" but he simply can't
> create a world without evil because he doesn't have the power over it.

That would mean that there is something separate from God. Which is
outside our definition of God. It would also mean that evil co-existed
with God prior to the Big Bang. As a separate entity. That would take
some doing. (Not that the Big Bang is necessarily the only model
available. I have no idea if the book _Stalking the Wild Pendulum_, by
Itzhak Bentov is still in print. Some of it is a little hard to absorb,
but he winds up giving a different model of the universe.)