Here God was not actually wanting him to sacrifice his son because he was the son of promise. Why would God want him to kill his son when he had already promised a great nation through Isaac? This was a picture of the new testament atonement, where God sacrifices his own Son for our salvation. God tells him not to do it and instead provides a lamb for them to sacrifice, which is a symbol for Jesus taking our place (Jesus is referred to as the lamb). "By faith Abraham, when he was tested, offered up Isaac, and he who had received the promises offered up his only begotten son, of whom it was said, “In Isaac your seed shall be called,” concluding that God was able to raise him up, even from the dead, from which he also received him in a figurative sense. (Hebrews 11:17-19). And of course there are many other lessons like Abraham's obedience, his faith, and so on. Animal sacrifice was important because it was a temporary covering of sin. But when you look at the instructions they were given (it had to be spotless etc.), you see that it all pointed to death of Jesus (See Hebrews 7:27). When Jesus died on the cross, he fulfilled the law and we're no longer required to do that because it was all a symbol of his death. When John the baptist sees Jesus, he says "Behold! The Lamb of God who takes away the sin of the world" (John 1:29) and in many other places he's referred to as the Lamb. As for human sacrifice, it's very clear that God does not approve. Whether the Hebrews practiced it or not does not mean that God approved of it - keep in mind that just because it's carried out by a "Godly" person, it doesn't mean it was from God. "And they built the high places of Baal which are in the Valley of the Son of Hinnom, to cause their sons and their daughters to pass through the fire to Molech, which I did not command them, nor did it come into My mind that they should do this abomination, to cause Judah to sin.’ (Jeremiah 32:35). There's also other places that show you what God thinks about human sacrifice. I think it's important to read the earlier verses in Judges 11 and see what transpired. The problem is that you incorrectly equate man's actions with God's will. God was going to give him the victory regardless, so the vow was unnecessary, God hadn't asked him to sacrifice anything to him. The lesson is to not make stupid vows. Another example that's often pointed out is king David's affair Bathsheba. He ends up killing her husband, which again, is not God telling him to go take another man's wife and kill the husband. You see that also in Abraham taking his servant and trying to fulfill God's promise of a seed through her. This wasn't the way God had intended it to be and as a result, we're still suffering from that bad decision. To me, the problem I see is that you're imposing your view on the text, when an exegetical approach will show that God is not happy with human sacrifice.