Sorry, but your interpretation of what happened with Abraham and Isaac is not accurate. First, the “God of the Old Testament” is the same God that we find in the New Testament, so if he’s a “scary dude” in one, he’s just as scary in the other.
There is nothing in that story in Genesis 22 that indicates that Abraham was “in terror and grief” over the situation. He is presented simply as a man who was doing what God told him to do without questioning God’s motives. He had faith that God would provide a substitute sacrifice to take Isaac’s place. That is why in verse 5 of Genesis 22, it says “And Abraham said to his young men, “Stay here with the donkey; the lad and I will go yonder and worship, and we will come back to you.” Abraham is not lying to these men to get them to stay behind so he can go kill his son - he has faith that he and his son will both return to the men as he stated.
In verses 7 and 8, we see the following exchange: “But Isaac spoke to Abraham his father and said, “My father!”
And he said, “Here I am, my son.” Then he said, “Look, the fire and the wood, but where is the lamb for a burnt offering?” And Abraham said, “My son, God will provide for Himself the lamb for a burnt offering.” So the two of them went together.” Again, this doesn’t sound like a man who is grieving, having trouble holding himself together. He is calmly obeying God in faith that God will ultimately not force him to kill his son, this great promise that was delivered to Abraham and Sarah in their old age.
Indeed the Lord did provide the lamb for the burnt offering that day. And the Lord told Abraham that because he had shown that day that he feared God, he should not lay a hand on the boy. This doesn’t mean that Abraham did what he did out of some sense of obligation to God or some sense of sheer terror of what God would do to him if he didn’t comply. It just means that he respected who God is and knew that his son was a gift that came from God in the first place.
That’s why, in verses 17 and 18, God makes an amazing promise to Abraham, a promise that all the nations of the world would be blessed through the seed (Isaac) of Abraham.
I’m not going to post it here because it’s so long, but please read Genesis 17. This is the best explanation I can give of the fact that Abraham knew that God would not require him to kill Isaac. In Genesis 17, God tells Abraham about his future son (Isaac) and the promise that will be fulfilled through him. Notice that in verse 19, God tells Abraham that Isaac will have descendants. If Abraham believed this to be true (he did), then he KNEW without a doubt that God would not allow Isaac to die before this took place. At the time of the events of Genesis 22, Isaac was still a young boy (he is referred to as a “lad”. He certainly didn’t have any descendants yet at that point, so Abraham had confidence that God, who ALWAYS keeps his promises, would keep this one as well and would grant descendants to Isaac through which the nations would be blessed.
The best part of this whole story is the ram that was caught in the thicket, which is a clear picture of Christ - the substitionary atonement for the sins of those who would believe in him.
YMMV