You're entering the territory of the problem of evil now.
The girl that got killed is now in heaven. She got lucky before her father did. It's a narrow view to think "God didn't stop this". God clearly commands against such actions, but her father clearly went against that anyway.
The first guy went to heaven, and so did Lot's wife. You're forgetting the context of what death is.
As for the young people that were mocking Elisha, they were literally telling him to "go up" and essentially die. He uses God's name in vain. The action isn't endorsed, and there's similar cases of moses doing it on a smaller scale.
The Bible shows where it's prophets and apostles flaw and err. And it's important to document these flaws. The overarching story here is that perfection came through Jesus- not the patriarchs, prophets, apostles, or priests. To just isolate random instances and get offended at them is very shallow. It doesn't even make sense as an argument against the text or God- you can't really say "god doesn't exist because I disagree with him". And if God exists and you disagree with the literal author of mortality, the universe and mankind, you're the one who's wrong. These stories have no bearing on God's existence. God gives us our life and can take it away whenever He pleases. The fact that He is patient enough to let us live is in itself showing His mercy - considering that we do little other than rebel against Him constantly.