Back to the OP:
If it makes you feel any better, one is only able to do about 30% of what you've trained under stress. That perfect kick or punch isn't likely to happen. If you land a punch, it could be glancing, etc. Also, one punch, one kill is nonsense. If it weren't, people would die in BKB matches all the time, but they don't.
Generally speaking, good boxers and wrestlers aren't going out and starting street fights... they're too busy training, and they don't want to risk injury for something stupid.
If you get into a situation where you have to fight, you've already made a lot of mistakes.
Enjoy your art, and be rest assured that without a lot of intense, resistant training, you're unlike to seriously harm anyone with it, even if you wanted to. A seasoned thug is much more dangerous than the average martial artist.
And yes, learn to wrestle: collegiate wrestling, judo, bjj, catch wrestling, chin na, anything like that. Otherwise you're a sitting duck if someone decides to take you down and beat you senseless. You don't have to be a submission artist; you need to be able to stay standing, and defend yourself if you end up on the ground if Plan A fails. Personally, I have found Judo to fit my needs well in that regard, and some people find it blends well with karate.