there's quite a bit to cover here, but ill try and keep it concise.
i can only recommend from my own personal experience, but as a practitioner and instructor, i have trained in several martial arts, all of them with merits of their own.
Primarily, in terms of self defense, i would recommend Krav Maga. It is a fairly comprehensive style that doesn't require you to utilize your body in such a way that you have to force it to do things its not used to or in some cases meant to do. It also does not require you to "retrain" your brain as much as other martial arts may require.
your brain is hardwired a certain way. the subconscious fight or flight response will always want to do certain things in the interest of self preservation. some martial arts occasionally train you to re-task or even ignore that response, which can take a lifetime to effectively utilize. Krav Maga utilizes this hard-wiring, and instead of yanking it out and replacing it bit by bit in a different way, it makes small adjustments to your natural reaction to a fight or flight situation, making them exponentially more effective though training. After a fashion, you already know most of what Krav Maga has to offer, but in taking classes you can perfect that knowledge and turn it into a valuable tool.
however, make no mistake that when a situation arises that may result in violence, always look for the option that will result in either a peaceful resolution, or simply remove yourself form the situation altogether. life is not a kung fu movie, and regardless of what you may know, you WILL get hurt in almost any kind of violent altercation. it is an unavoidable fact of combat. there is no invincible, so if you pick a fight, be prepared to walk away with injury.
remember that as always there is no shortcut to learning, and you will have to apply yourself as much as you would in any other art, but In my opinion and experience Krav Maga produces the most effective and immediate results in the time that you spend learning it.
Hope this was helpful, good luck in your travels, and have fun learning.