God does not follow the first principle of morality. Why not?

[Drich]

Well, so far it doesn't seem like he lives up to my non-absolute standard.

Exactly! Why? Because you/the soceity you live in has created a standard in which you can view yourself as a 'good' person. Now you have taken that sub standard, standard and judged God with your/our soceitial short commings as if this was any real type of measure. Of course God falls short. If He did not in your own standard then that would mean you would. why look at your failures and faults when you can blame a seeming silent God?

God is on his own (alleged) record as having committed terrible crimes against humanity. I don't know how that isn't a huge problem.

Because 'Humanity' belongs to God. The lives humans live belong to God. As Creator God has rights that you do not. Giving and taking life is one of them.

What I wonder is, where does God's righteousness come from? Himself?

Yes.

Does that mean his will is completely arbitrary?

As in God's will is righteousness.. Yes.

If so, what is our motivation to submit ourselves to it?

Why do you need one? God's Will is only for those who wish to spend eternity with Him. Those who do not, do not need any motivation. God's righteousness is an 'arbitray' line in the sand. Those who wish to spend eternity with God must seek attonement for being outside of God's Righteousness, and those who do not simply stay the course.

Is it because he is more powerful than we are?

Yuup!
God's creation. God's rules, and there is nothing you can do about it..

Because, that sounds a lot like that survival of the fittest thing Christians seem to think dominates secular morality.

Ahhh, no. Gay marriage, Abortion, the promotion of prematerial sex, the soceital push to allow us to think we are 'all basically good people.' these are not "Christian values."

You tell yourself God is good because you're too terrified of the monster to say otherwise.

God is Good for no other reason than He defines what 'Good' is.

I know that spinning God as ultimate good and loving everybody makes it easier to sell the bullshit, but I'd honestly have more respect for his followers if they were honest and admitted that God is neither good, nor perfect, and that their 'personal' relationship is one of existential terror.

Fortunately we do not need the respect of those who wish to compermise our faith in order to award us with 'peer approval.'