Why cant you ask God for proof? i do all the time, i ask for assurance, and confirmation, and He gives it to me, sometimes after i have completely forgotten i asked. glory be to him,
There is a great example of this in the Quran, when Abraham asked God to 'show me how you give life to the dead'
So he did.
Praise be to God, what an awesome God we have.
also God revealed his criterion, and all his revelations, as 'a guidance and a mercy for those who trust'
hence, when God says do not kill, unless in justice, i would follow that, god willing.
Dreams can easily be manipulated i believe, i think that God sometimes gives us guidance, or premonitions etc, as i have experienced this, but also sometimes they seem just completely random, and also often satan can misguide is with things like confirmation bias, etc not only with dreams, but i think especialy, due to the abstract nature of them.
Peace