Should I retake GRE given my situation about university deadlines?
I don't have any strong opinion about which date is better for you. 

I also don't mean to be unkind, but you should first address why it is that you make "silly mistakes". Your question here is full of them. 

But I imagine that one cause might simply be that you rush through things without taking the necessary care. The solution is to slow down a bit and consider what you write or answer before reacting. 

If someone is brilliant but sloppy they may have less of a future than someone else who is competent but methodical. 

But, apologies. I'm not trying to be mean or insulting.