I have a ton of respect for the art of Aikido, don't let my comment confuse you. But, in my experience, (what little I do have, bar fights, etc.) Aikido had limited practical application until higher Dans.
It's too difficult to use such fine motor skills when in the heat of the moment.
So devote the time and effort necessary. You sound like someone who seeks instant gratification. There is far more to martial arts than being able to punch one's way out of a bar fight with a modicum of training. If that's all you want, you'll be missing a lot, like 90% of what martial arts is.
But given what you seem to be describing, find a boxer and take private lessons. You will be able to effectively defend yourself in short order.