Raggie,
First, it doesn't make sense to me that one should put himself in a position where the likelihood of either being mugged or having to shoot someone is high.
You might prefer to walk at night when it is cool, but it will be a small matter if and when you are assaulted, regardless of the outcome. I agree that you have a right to walk at night, and should be able to walk anywhere you desire. However, there is an element of common sense, which dictates that you not increase the risk of danger to yourself for the convenience of walking in a dangerous place at a dangerous time. I would, and do insure that I do not unnecessarily place myself or others in a risky situation. Our society, and the law make it difficult to dissuade the thug in advance of his crime. The law will attempt to catch him, but it may be too late for you. You are essentially on your own.
I personally believe, that regardless of where I live and walk there are always those who wish to rob or harm others. I determined many years ago that I will not be a victim, or at least an easy one.
It may be impossible for you to get a license to carry a firearm. If you can do so, you might want to go through the necessary training and get a weapon to carry. Even then, however, retreat is always the best option if it is reasonably possible.
I would not, even when carrying a firearm, go where I thought the odds were relatively high of having to use it if I could avoid it.
Each individual must make that decision for himself, and weigh the consequences of his actions.
Good CS spray is an option, but the wind direction and other factors may make it relatively ineffective, and especially if you do not have the best and also know something about its use. Fox is among the best, and very effective, but it is necessary to understand its use, and to make sure it does not disable you also when you use it.
I doubt that anything less than a firearm is going to be very effective considering your size and lack of training. Knife combat requires much training.
Use your head, and as has been said, that is your most effective defense. In using it, DO NOT unnecessarily expose yourself to danger. Find another place or time to walk.
Jerry