I've been struggling with belief in God since October 7th. Is it ok to be angry at God?

What you are describing is not a failure of faith; it is the cost of caring. After October 7th many deeply committed people found that their old, simple picture of God broke. That breaking is painful, but a faith that cannot hold horror was always going to crack the first time the world showed its teeth.

Our tradition does not ask you to pretend. It hands you the language of protest — Iyov, Eichah, the bitter Psalms — precisely so you have somewhere to put the rage without leaving. Bring the anger in, into davening, into learning, into the room. A God who can be wept at and even shouted at is a God still worth standing before. Give yourself time; faith after trauma is rebuilt slowly, and often it comes back deeper and less naive than before.