What to do if I warned my landlord numerous times over the phone about the safety issues in my neighborhood plus the threats I received and I was then assaulted?

Unfortunately, your landlord is not responsible for injuries or conditions beyond his or her control. That includes the criminal activities of third parties who are not under the landlord's control--that is, criminal activity by anyone who is not a tenant or employee of the landlord. Therefore, since you are concerned about safety issues "in your neighborhood," you presumably are concerned about safety issues outside your building; and if you were assaulted "in the neighborhood," then presumably you were assaulted by somone not connected with the landlord.

If this is indeed the case, the landlord bears no liability or other responsibility for this. The landlord does not have to respond to your concerns about the neighborhood any more than he would need to respond to your concerns about the economy or the government; you have no grounds to terminate your tenancy early; and the landlord does not owe you any money and you have no grounds to sue him. If you do move out early and cease paying rent, you will be in breach of your lease and the landlord could take the unpaid rent out of your security deposit and--if the deposit does  not cover all the rent you will owe for the remainder of the lease--sue you for the balance.

Simply put, the neighborhood's crime is not your landlord's issue, just like if there was crime near where you work or shop, neither your employer nor the store owner would have to do anything about it. Your concerns should be addressed to the police and city council, not your landlord.