This is the point in question: Is it in God’s nature to command mano a mano killing. That is the OP’s question and the consistent question of atheists and those scandalized by Christian fundamentalism.
Let me put it this way, since looking more closely at Deuteronomy, my view slightly changed. In short, no. This isn’t quite what God is doing, because when you look carefully, Deuteronomy mostly consists of Moses giving the commands to Israel, whereas in the rest of the Pentateuch, we see the commands as stated by God to Moses. However, what he did do was give Moses an authority to command his people, and what Moses commanded, with God’s blessing, was Deuteronomy. This does remove God from the commands a bit, but it still is a hard passage. Modulo this slight tweak, I see my interpretation as consistent with what the Church teaches.
If this still does not satisfy you, go to Deuteronomy 20, which lays out the stipulations of Harem warfare, and give me a proper interpretation, one which manages to do the job of 1) getting accurately what the author was trying to convey, 2) is consistent with God’s goodness, and 3) does not attribute error to what the author was trying to convey. You cannot brush aside the uglier details of these commands, because these details are relevant to the whole passage. So far you have condemned every attempt to interpret this passage, but have not yourself provided something that works. You are afraid of scandalizing the non-believer, but sloppy attempts at interpretation only indicate to him that you are simply in denial about the hard passages. Go ahead, have at it. Get your hands dirty with the text and see what you can muster.