How do we deal with the parts where God commanded…

How do we deal with the parts where God commanded the Israelites to kill everyone in Cannan and other places? How do we deal with the wanting of sacrifices of innocent animals? Why did he say to sacrifice Issac if he never thought of child sacrifice? Why create the devil? Why create the tree of the knowledge of good and evil?
Have strong faith but these are the issues my family and I have been seeking answers to. Want resolved.
EDIT:
So new topics… If the devil was a murderer and theif from the beginning, how does that fit with the theory that he was an angel that fell who was once perfect? The king of Tyre may not be the devil then. He is a cherub it says. So was he made before time and the beginning? How could he have been perfect and then become evil if God says he was a murderer and theif in the beginning?
The Cannanite infants were innocent, why kill them and not save them? If the Cannanites were to be killed for killing their infants, why would he command the Israelites to do the same thing to these infants instead of saving them?
If God hates the hands of those who shed innocent blood, why would he command them to kill innocent infants? Why would he command to kill and shed blood of innocent animals? This seems like a contradiction and needs to be addressed or it is too easy for unbelievers to pick on.